Have a word.
A calm one, as that increases the chances of him taking on board what you’re saying.
Expect him to be defensive because it’s an instinctive reaction, but don’t assume from that that he won’t think about it and take it on board.
(I had a woman once tell me I was driving too close behind her as we both drove through a speed bump riddled industrial estate to our mutual place of work. Despite responding with some sort of withering and dismissive retort, and although in this instance I still don’t think I was too close, I did modify my driving in that area from then on to avoid distressing her and her ilk again. My point is, even if he responds like a dick, he might still take it on board 🙂 )