I don't think it was Petofi's motives that were evil (I agree he can't really be blamed for looking out for his own survival), it was his way of doing things or getting things he was after that were downright despicable.
[spoiler]1. he possessed Jamison in order to force Quentin and Magda's (excuse the pun) hand to get the hand.
2.He had Aristede abduct Quentin as a plot to force Angelique to return the hand to him (whether Petofi told Aristede to trap Quentin under that blade or that was purely Aristede's idea I don't know).
3.He kidnaps Julia and threatens her with the hand unless she tells him to go to the future (then when things don't work out and Julia tells him the truth he doesn't believe her and sics Aristede on her).
4.Knowing he must have a body that's already alive in the future in order to go there, he steals Quentin's.
5.He set up Magda with the fake hand when King Johnny around to throw him off track (and knowing very well Magda would be a dead woman for certain when Johnny saw the hand was a fake).
6.He makes Jamison possessed with the spirit of David in an attempt to force Barnabas to reveal how he go to the future.[/spoiler]
Petofi was no innocent babe in the woods for sure!