If he really was a tech, he would have seen you had a official license for Avast and would have left it there.
Little true story:
Someone has problems with the comp. The neighbour takes a look, but can't solve it. Be hé no problem the neighbour knows a real comp tech. He calls the guy and let him come over. People come over to my store with their problem and when they tell me this I say "if it really was a tech, then why are you here?" And another funny thing about this is that I many times can solve the prob that the "tech" couldn't within 30 minutes, while the customer waits and drinks his cup of coffee.