This isn't a good argument for banning Mew. Mew might be able to run a billion sets, but if every single one of those sets has solid counters, then it is not broken. This is not to say that versatility doesn't matter (it does, a lot of people make that mistake with suspects) but rather that versatility should not be the predominant reason for the suspect's banning.
When I look at Mew, I acknowledge that all its sets are pretty badass, but I find that each individual set should be easily handled by any decently prepared team. If you're weak to NP Mew, you're probably also weak to NP Azelf and NP Celebi. If you're weak to stall mew, you're probably also weak to stall missy and taunt deoxys. The fact that mew can run both of these sets is irrelevant when you should be fully prepared for similar sets from other Pokemon anyway, not to mention that you should have a rough idea of what set mew is running just from the kind of team it's in (a mew on a team with ninjask probably isn't going to be a sweeper variant).
That said, it's entirely possible that someone will come up with a mew set that breaks it. Stallbreaker mew comes really close in my opinion, I can't count the number of teams (and not just stall teams) that have ragequit because they can't get past it. But until someone nominates one or two specific mew sets as "broken" and only then says "its versatility adds to its brokenness", I wouldn't vote it BL.
