That's because these people can't say it directly that they hate the game, they make reason so they sound intellectual when in reality they're hypocrite for hating slapping matches when at the same time they're enjoying boxing and other contact sports that tends to get much bloodier than slapping.
it's not that I hate the game but I do understand their concern. I guess their primary concern is that the people who join the tournament aren't properly trained to take that much force in the head multiple times in a row. also, one of the concerns I see is that people that are clearly should be in a different weight category are being matched up to each other. I understand that the people who joined the tournament know the risk but that doesn't make people's concern about the risk of the game less valid. I love contact sports, martial arts, but seeing people who aren't trained do this is a little unnerving for me but that doesn't mean I hate the game.