Well, 'sports' itself is predatory and causes lots of young people to trash their health for the amusement of onlookers.
I say 'sports' to mean the stuff people watch on TV and in stadiums. You going for a run or kicking a ball with friends is fine. It's audience-driven sports that are bad.
A bit of betting is small fry by comparison.
A few thousand athletes making millions of dollars being amusements for onlookers
vs
tens of thousands of people ruining their financial lives from gambling