Apologies for my English.
Some thoughts from the camp of idealists. :)
The following is the explanation of the question in the title.
I think that the fact that in our days physicists may be materialists or idealists does mean something. It means that physics itself can't claim by proof or evidence which ideology is true or false.
Ideally, all empiric sciences should be no more than a synergy between empirical evidence and maths. They really shouldn't be taken as tools that by themselves are capable of providing ontological proofs.
One brilliant materialist, Bertrand Russel, wrote:
Of course it is not by argument that we originally come by our belief in an independent external world. We find this belief ready in ourselves as soon as we begin to reflect: it is what may be called an instinctive belief. We should never have been led to question this belief but for the fact that, at any rate in the case of sight, it seems as if the sense-datum itself were instinctively believed to be the independent object, whereas argument shows that the object cannot be identical with the sense-datum. This discovery, however—which is not at all paradoxical in the case of taste and smell and sound, and only slightly so in the case of touch—leaves undiminished our instinctive belief that there are objects corresponding to our sense-data. Since this belief does not lead to any difficulties, but on the contrary tends to simplify and systematize our account of our experiences, there seems no good reason for rejecting it. We may therefore admit—though with a slight doubt derived from dreams—that the external world does really exist, and is not wholly dependent for its existence upon our continuing to perceive it.
After some thought and study it should be obvious that something independent of our perceptions has to exist. Our perceptions obey the very complex and somewhat stable Model (I'll uppercase the first letter of this world to distinguish the meaning when it's not obvious). The only narrow part of this model is studied by physics.
Materialistic (or physicalistic in modern terms) approach seems to suggest that the model and its submodels that rule all our experience are derivatives of objects that exist in time and space, and there is nothing except these objects in time and space. And these objects, including time and space, by themselves obey some rules that bit by bit are learned by physical science.
This approach is a model by itself. It's obvious that it is inspired by habitual mental templates which are partly inspired by the Model itself, since our perception loops behave like there is an independent external world which is similar at least in time and space to how we perceive it.
Well, try to use the materialistic model on virtual 3d worlds like those in PC games, and it will become obvious that this approach will not only bring an unnecessary complexity, but will bring us to a completely misunderstanding of the infrastructure for such virtual world and to a totally false ontology!
It seems that at some point in future it will become technologically possible to translate virtual worlds directly into perceptions via interfaces known as brains. After that it will be much harder till impossible to distinguish between the 'real' world and the 'virtual' one.
The much more simple way is to recognize: all that is required for our existence is a 'screen' as a 'place' for our perceptions (from colours to thoughts), a model for regularity, and something to produce the both.
The materialistic approach requires the 'screen' (brain) and a model (physical rules) too, but it also requires a zillion of unnecessary things + something unknown that would be a reason for all these to exist (like a reason for the Big Bang).
Occam's razor rests in peace.
As for qualia like colours, sounds, pleasure, pain, etc.. - I personally didn't found how the suggestion that they are nothing more than physical objects can be consistent.
Let's talk about colours. If they are nothing more than waves with certain frequencies then we should see colours before these waves reach our eyes. Because after that these waves stop to exist as waves. If colours are nothing more than affected by those waves groups of neurons then these neurons must be coloured with the perceived colours for something that is capable to perceive these neurons as colours in exactly the same form as they're seen by a person. In this case this "something" would be or the same coloured neurons, or some other neurons, or something else. If it is the same coloured neurons, then we're going to conclude that colours are perceived by colours... If it is some other neurons, than colours as they're seen are in those other neurons, thus the coloured neurons aren't really colours... If this is something else, then we should look for some other physical entities, but for any candidate the coloured neurons won't be the colours themselves. In general, the problem in the materialistic approach, that it requires some physical entity to be a colour as it is seen, and some (maybe the same) physical entity to actually perceive this colour. If a colour and a percipient are the same entity, then a colour is seen by a colour. If they are different entities, then the perceived entity exists in the perceiving entity as the colours exist in us when we're seeing them. Thus, if we aren't radically different from our brains, then some parts of our brains should be coloured literally - otherwise they aren't colours. In short, the requirement for some non-colour to provide colour leads to nonsenses.
Obviously, there is a mapping between different colours and measurable properties of light waves. But it seems to be nothing more than a mapping, provided by the Model. And maybe, this mapping is different for different persons - if such different mappings provide the same regularities within the Model then we can never know that some person sees green while other in the same place and time sees red or blue.
Now, substitute the term "colour" with "sound" - what physical entity would be a sound in our brain as we hear it? The same seems to be correct about other qualia including pain and pleasure.
P.S. What we actually perceive is a somewhat ordered set consisting of its subsets that constitute different kinds of data like colours, sounds, feelings, thoughts, etc.. This set is regularly changing, and whenever we point at different subsets in different times and state that they represent the same thing - we abstract from differences and populate our mind with objects of the so called "external world". Thus materialism seems to be a belief that these abstractions must exist by themselves. For whatever reason.