Are you saying that tor exit nodes are generally malicious? I mean, I understand the precautions involved in routing the data like that, and that there's the possibility, but is it really that rampant?
Regardless of the real situation, it is to be assumed.
My understanding is that its the vast majority.
Tor is a very attractive target for such behaviour. It takes very little effort to set up a Tor exit node and to start passively sniffing traffic. It would surprise me more to find out that this behaviour wasn't rampant.