Word of mouth, but if you looked at their twitter and proof presented it was undeniable. If you want to go digging check a french contenders player that there are videos of with an instance of where the aimbot bugged out and started aiming directly at the center of a player with perfect reaction time and movements.

Every other competitive game regularly has public cases of cheaters being caught in pro games, overwatch doesn't.

Wait... Your proof that something has happened is that there is no proof?

Do you really think that's not sufficient for the purposes of this conversation?

Absolutely not. Making wildly speculative claims and saying that the lack of proof of it not happening is conspiracy theory territory

Why do you think this claim is "wildly" speculative as opposed to merely speculative?

We have two possible options here, it's pretty obvious which is the more likely one.

It is pretty ridiculous to suggest that nobody has ever been caught cheating in overwatch pro games.

Again, you are missing the point, just because something is "likely" to happen doesn't mean it did happen.

What you are basically asking is that we should provide a "negative proof", imagine me going through all the pro matches to prove my point that it did not happen (going in this extreme) when you can just show me a proof that it did happen.

“Trust me bro”