Why do not you buy ETH on a exchange(polloniex, cex....)?
He's right, it's weird as a request, buy ethereum on btctalk..
If you need proof i can sign an address that i own that i posted here
https://bitcointalk.org/index.php?topic=601965.msg6996129#msg6996129Create a thread in scam and accusation section about your issue then only moderators can help you lock the concern account you lose with him.
Then you please write with the reference in his trust and rating of this person.
@op if you wish to buy a ETH, Please refer the below reddit thread which has been created for the same information.
https://www.reddit.com/r/ethtrader/comments/5yr750/best_place_to_buy_eth/