Completely agree. But do also agree that there is a way to overcome this. An Everton fan came in first in FPL several years ago on the hard rule he would never select a player from Liverpool. Klopp was already there and it was insane to think not selecting a Liverpool player. Kudos to him. He came first anyway. I also agree that betting on games involving your team is a mistake. But here's where I will say it isn't so bad to bet on a rival team: It lightens the blow when a rival wins. I myself make better decisions involving teams that aren't my own. But it does give me a situation where if the rival team lost, well it's good for my team. If they won, well, I win money (Assuming that was my expected outcome). I will say the only thing that can really put a question mark on your fanhood is betting against your own team. Which is exactly why I would never do it. That combined with irrationally betting for them. And in the biggest games where my interest is already high anyway, I tend to enjoy the game great without needing to bet. But where betting is nice is I never bet much. But by betting a bit on the odd games it increased my interest in the sport as a whole. I used to only watch the EPL. I watch a lot of La Liga and Bundesliga now as well because I bet a small bit just to have an interest on the game and I became a bigger fan of the sport for it. Even games involving lower half EPL teams I used to not watch but will now for that reason. So there are positives to betting on the odd game.
RE: Do you agree that FPL and betting are making football loyalty harder to come by?