Sports, especially for kids, should be about fun. They should learn proper teamwork, dedication and have fitness and fun. If I was put down by my swim coach like that, I'd tell him (or her) that this was not acceptable and I would quit the team, as much as I like swimming.
It is also good if the kids get a say in whether or not they participate in a sport. There was a time (either last year or the year before, I cannot remember) that I really wanted to quit swimming. My parents let me not swim for a while and now I'm back-on my own choice, not their's. If Vladi doesn't want to play football, which it sounds like he doesn't, it's not the best idea to force him to. If you really feel he needs to exercise regularly or play a sport, try looking into other sports that he may enjoy. 
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Itaque incipet.
All that glitters is not gold but at least it contains free electrons.