Leaving negative/bad feedback

If you are absolutely sure this guy is selling stuff on Ebay by being dishonest I wouldn't hesitate a second to leave negative feedback.....but only after I contacted him and got his side of the story.

Every time I buy something on Ebay I check the feedback before I purchase it, especially if it is >$100. There is always going to be some miserable person out there who is never satisfied and those types are pretty easily spotted in the feedback. But if there is a pattern of problems, that guy doesn't get MY money. But since everyone is just leaving neutral or positive feedback these days it makes it harder to spot the crooks, the lazy, or the genuine POS sellers who depend on their customer's empathy to continue doing business online.