Having lived with a sociopath I've had to learn the hard way that the best way to deal with people who take great delight in tearing others down is jut to ignore them and not give them a weapon - don't let them know that something hurts or upsets you, don't give them a reaction or they'll just keep doing it. Shut them down, turn the conversation onto something mundane and keep your chin up =) I'm glad you have someone to talk to about this though as that support is priceless =)
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