I have a 16-year-old son. I’m in my early 30s (had him very young) and a professional footballer. My son also dreams of becoming a successful footballer (he’s been playing since he was 6), but he’s just… not great. He’s good, but not great - and in this extremely competitive industry you need to be at least great in order to even stand a chance. So I told him, as someone who’s been doing this for a very, very long time & is active in this sphere, that he should find another, more attainable dream. He took it as me not believing in him, but I’m just objective and realistic.
Looking at this with adult eyes, no I don’t think you’re a jerk. It sounds like you’re trying help him see the reality of the situation before it causes him any undue emotional (or financial) suffering. It’s not, however, very hard to imagine how from his point of view he might feel like you’re being jerk, or maybe a bit hypocritical.
Is there any way you can get him playing with kids who are good enough to go pro? If he can start playing against people who genuinely have the goods, it’s probably not going to take him very long to figure out for himself whether he can keep up or not. And that way you don’t have to set yourself up as the bad guy as much, and you can play a more supportive role and be there to guide him to an alternative path once he gets sick of the other kids running circles around him. At least that’s how it worked for the couple of kids I knew growing up who were good enough at basketball or American football that they really thought they could go pro. It was playing against people who were the real deal that made them realize they didn’t have the shot they thought they did. It was pretty obvious that these other kids had something extra, and were playing on a level my friends felt they were probably never going to reach.