I have never seen a chance like this for a bet.
I mean, yes maybe I have seen some racism during a match (like Milan Goalkeeper some months ago) but nothing that was directly linked to a betting game or that was able to change the result of a match. of course racism should be blamed and boycotted.
I will not consider gamblers as "part" of the issue. Some times it's also not possible to detect racism only by following the match.