I think it's going to depend on what you then plan to do with those views. Specifically, are you taking them as valid or invalid assumptions for doing ethics (i.e. will you knock them down or does your paper focus elsewhere and take them for granted?)
If my goal is to attack a common place view, then it really helps to have some evidence that the view is common place. If you can't get that, then
In the Modern West, many people intuitively believe that ...
(bears some weakness on dubitability but ...)
It is commonly held that ...
(Weakness of where? who?)
If you are going to grant these claims and focus elsewhere
I will take it for granted that ...
(you can add the common place somewhere in there but it's not absolutely necessary).
While argument can be made for and against, I will for the purposes of this paper work under the assumption that ...
In this case, it's wise to pick assumptions that make your argument harder in which case you can add:
I do so because if I can prove my claim under these conditions, it also obtains without these assumptions.
A good place to look is Peter Singer's "Famine, Affluence, and Morality" where he artfully uses views and positions that aren't his to highlight the effectiveness of his claim even outside his framework..
For the first category, famous citations and statistics help (I would suggest for instance Kant's views on animal suffering as a place to start). For the second category, you don't really need them. Depending on the scale of where you are trying to make these claims, this is not the most important thing to focus on. (If you are aiming for a journal, try to see if people in that journal generally concern themselves with (a) empirical surveys when they mention common views or (b) like famous figures or (c) gleefully say things like this without citing anyone).