artists_beware | I need advice regarding a troublesome user.

Hi all. I recently took on an art trade in exchange for a ref sheet of my character.

They got someone else to draw my character (since they can't draw themeselves, but wanted art from me), and I will be drawing theirs. I started on my half of the trade today via a LiveStream so the tradee knows good and well I'm doing my half. Their half of the trade was completed quickly so no worries there.

Well, also today, I found out that this person has a really bad history of being incredibly rude and demanding and selfish to other artists. Some people on Nabyn noted me and told me this and that I should stay well away from this person. This person has also gotten banned on FurAffinity and had created ban-evasion accounts which have been banned too. On their deviantART account, they also cuss out and complain at people who thank them for watches/faves. I don't believe this person is a troll, just incredibly rude.

Example: http://i.imgur.com/7xa5h.png

I also found out that this person is going around telling people they'll put me on here just because they think I was "avoiding them" for the last two days (when in reality I have been busy and not much in a IMing mood). They have also been going around saying I was a "con artist" and that I'm not planning on drawing them anything. The person claims I am his friend (I have only know this person for a few days!) so maybe if I block this person, they'll try to use the "I thought you were my friend" excuse. They are also a liar, claiming I said things when I did not.

Unfortunately, I didn't know this at the time I accepted his offer, otherwise I would have told them no.

What should I do? Should I finish the trade, and just remove him and block them? Or should I post them here? My friend also told me that he had a really awful experience with that guy as well and he wouldn't mind coming here and telling his half of the story. I have screenshots of the evidence proving that this person is disrespectful to artists and some chat logs.

EDIT: This guy is starting to make block evade accounts and note me and is making call out journals on these accounts. He is also IMing my friend and attacking her as well.