Personally I agree with the OP in that those people who spout the "footballers are overpaid" line seem to me to be quite stupid, or at least hypocritical.
Such people seem to single out football for their criticisms unfairly: they don't, apparently, have the same problem with other industries which attract millions of pounds of investment because they are vastly popular, such as the pop music industry.
Many times I've heard people say "they get paid millions just to kick a ball around." Firstly, you can reduce any activity to absurdity if you really want to; that's just mindless rhetoric. I could say Lady Gaga is paid millions for shouting into a microphone, or bankers are paid millions for doing a few sums.
The fact is that in a capitalist society, money goes to where the demand is, even if that demand is for something that seems pretty simple, like kicking a ball around. 'Cos even if you have no time for the sport yourself, you can't deny that it is massively popular with many other people. I was quite taken aback when my A2 Lit class (which was 95% female - and not to discriminate against female fans but girls don't tend to like football so much from my experience) agreed that in an ideal world they would ban football, and they were serious! I just thought OK, it's fine if you don't like it, but you should respect the choices of other people to spend their lives doing what they like.
If you want to argue against the capitalist principles that make football the way it is today, that's one thing, but it seems like people just single out football for no good reason.