Surely he must take this seriously considering the evidence outlined
Are you going to address the question as to whether your account is an alt? You don't have to name your main accounts, but it would be nice if you'd disclose that you have at least one other account.
I don't see how this is of any relevance to what the OP is saying. Especially considering that based on the rest of your post, you already have a preconceived answer, and will either call him a liar (and not credible) if he denies having another account, or will call him a sockpuppet (and again, not credible) if he says he does have another account.
We already know the answer, but I'd like to hear it from you