Humans express their right to free speech through bots. It's no different from expressing your right to free speech through paid advertisements.

I think I am okay with contents from bots if they are marked like advertisements ("sponsored contents", etc.). For example, "post from ABC" could instead say "post from ABC, a bot account of XYZ".

I am okay with dishonest speech (or paid speech, for that matter), because it affects your reputation. Sockpuppets and bots harm reputation tracking.

Nobody in the real world - outside the ivory tower - actually cares about tracking the reputation of a PAC that was spun up for an election in order to run political ads, and will disappear in two months.

What makes a bot any different?

Not really. There are disclosure rules for paid advertisements. People can express whatever they want through a bot, as long as they also make it clear that this expression is being delivered by a bot.