Yes, one legit accusation is too many to be ignored.
Yes it is enough to call a black sheep what it is. If a casino has scammed once with proof and they keep denying it, they are likely to scam more unsuspecting player.
The solution is that except that they repent with proof , when someone is not repenting of a bad behavior they are likely to continue doing that at a little opportunity. In regards to feedback, except the casino redeem the image through paying the winning sum to the complaint, with apology and the complaint either comes public to the thread to announce the resolution and gives a positive feedback, then all other positive feedback backs amounts to nothing because there is no justice. Injustice done to one is Injustice done to all.