I've only done a very small amount of online dating...but I'm not surprised at all by the immature behavior the OP has encountered or heard about..bc there are plenty of immature, childish and entitled people around...

When you're dating period, It's smart and reasonable not to engage with people you're not interested in, for whatever your reasons are; but especially, if they've shown themselves to be petulant, pretty and vindictive assholes..