Poseidon was actually so hard to ragebait. But that's exactly why it was so much more fun to do it to him than to anyone else. Sure he barely every reacted, but whenever he did, it was like a reward.

Every time you could see his stoic expression turn in the slightest, his eyebrows furrowing just a little, his fist tightening, you knew you absolutely succeeded, even if it was barely obvious.

And so as you did whenever you got bored, you went to seek out Poseidon so you could get on his nerves as entertainment.