You're consenting to have your mind attacked with all the mental weapons at someone's disposal. This is a lot scarier because you're willingly giving up some measure of control over your state to the other person, however difficult it may be for them. You're also being attacked as yourself. The AI player is playing a role, and attacking within that role. Their own mental wellbeing is a lot less at risk, unless they think they've got horrible depths they never want to sink to.

to make a shitty analogy: It's like being at the top of a tower while someone tries to knock it down with their bare hands. Even if they have very little chance and have to expend a lot more effort than you, you're the one who's risking the greatest pain