Let's look at the translations (into first-order logic):

(1) ∃_{x} : Man(x) ∧ Married(x).

(2) ∃_{x} : Man(x) ∧ ¬Married(x).

The first is true in universes where there is at least one married man; the second is true in universes where there is at least one bachelor. To show that the argument from (1) to (2) is not valid, consider the counterexample: a universe with only one object, a married man. This is a counterexample because there is no bachelor in such a world. That shows the invalidity.

Now let me say a word about why I think you were thinking that this argument is sound or at least valid. Logically:

"there are φs" == "there is at least one x s.t. φ(x)"

e.g. "there are married men" == "there is at least one x s.t. x is a married man".

But colloquially, "some" is often used in a stronger sense to mean *only some*, so for example:

"sometimes I'm sad"

simply means that there are moments when the agent is sad, but it also *seems* to imply (in the literature they call this *implicature*) that there are times when she is not sad. To show that this is an implicature and not an implication, we can provide the following *defeater*:

"sometimes I'm sad; which makes sense, since I'm always sad."

It's kind of a silly example, but you get the idea. True implication cannot be defeated.