Is he stupid about other things or only when he does things that hurt you?
Most people are capable of understanding that hurtful behaviour is hurtful.
Abusers however, pretend not to understand. In order to make you feel like you have no right to be hurt. They may imply you are too sensitive or that you overreact. Or they may simply look at you with a blank expression, convering that they have no idea why you're upset.
It's bullshit.
It's a con designed to make you feel like you're the one with the issue.
The clincher? If you ever find yourself thinking 'if only I could just find the right words to make him understand (why his obviously hurtful behaviour is hurtful)' you are most likely, in an abusive relationship.
Now, if the behaviour isn't obviously hurtful, but instead, a personal bugbear then that might be different. But if that is the case, it should be a very rare occurance in the relationship. And, after you explaining once, should be understandable to him. It should be met with sympathy and understanding and apologies. And the behaviour should be not be repeated in future (provided that's a reasonable request) as he now knows it hurts you.
Most people don't want to upset their partners. They care when they do. They want to understand how it came about so they don't repeat the behaviour.
This guy...at best, doesn't care. At worst...knows what he did, meant to do it, is enjoying gaslighting you about it and making you feel you don't have a right to your feelings.
Life is short op. Consider who you choose to spend it with.