Just try to avoid the person and use the ignore option. All people have different way of thinking and also the maturity level is different depending on the age and life experiences. By giving importance to a person who is trying to put you down, you are giving him free publicity.

Regarding you mentioning that he is a merit source, that should not be done in public. If you feel that he is misusing the position of merit source, report it to the moderators with all proofs. As you have mentioned that he is a merit source, I think a lot of members will now try commenting on his threads or posts in hope of attention and merits.