what it seems to be is your opinion, and i suggest you keep it to yourself, because

1) you do not know me, or him

2) if you did, you'd know we're online friends, so me saying "yeah" to him isn't something new, and i doubt he would be offended or bothered by it. if you are bothered by it, keep yourself out of the conversation and don't make yourself look like an asshole

good day to you, sir