Ad hominem would be if the GP was making a personal attack on you. Saying a question is "silly" is not that.
Downvoting can also mean that the downvoter doesn't think it's worth the time to engage with prose. It's a bit arrogant to assume that a downvote means someone can't come up with a cogent argument against you; the fact that you make that assumption points even more strongly at the idea that it's not worth arguing with you.
Downvoting can also mean that the downvoter doesn't think it's worth the time to engage with prose. It's a bit arrogant to assume that a downvote means someone can't come up with a cogent argument against you; the fact that you make that assumption points even more strongly at the idea that it's not worth arguing with you.