Exactly. There is always someone who will be affected by slogans like that.
I saw a t-shirt in a 'boutique' last week that read "I'm sorry I was blind drunk and thought you were your fit mate" and underneath it had something like 'should have gone to SpecSavers' or another twist on the SpecSavers adverts.
How charming is that? And you can bet that some 20-30yr old will find that hilarious. Not giving a second thought to anyone with low self esteem that may have been with a guy like that.
And then we have the flip side don't we? We have t-shirts for women/girls that 'dis' men/boys but maybe not in the same way, not in the same ball park actually as these from TopTwat.
Is the uproar the same? I'm not being arsey, not at all, I hate these t-shirts. I just wonder if when it's the other way around, do men kick off or do they find it funny?
So if a woman wore a t-shirt saying 'my other man is a body builder', would men find that offensive or funny. Or if they wore a t-shirt like the ones that someone linked to here (the alternative ones up thread) would they campaign to have them removed?
I'm not sure they would you know. Because they just don't get it most of the time. It doesn't register like it does with victims of these situations being used as 'light hearted' entertainment! 
For the record, I don't like these kind of t-shirts for either sex.