Is it normal for someone with dementia to keep pooping their pants?

This seems to be a problem many patients and the loved ones who care for them struggle with. It is not something you can train the patient not to do, insist on protection, make them clean it up, or punish them for.

All you can really do is try and stay ahead of the game. Try setting a toileting schedule and get the patient to the bathroom every so many hours. Try to introduce protective garments early in the process while there is still some understanding. Not unusual for a loved one to refuse those garments so buy sex appropriate colors if you can and try removing regular undergarments from the closet. Worst case scenario obtain one piece garments that are secured down the back.
Another approach is to poop proof the house or at least the part of it the loved one has access to. This means removing any unnecessary furniture and protecting everything in use with waterproof material. if you notice in a hospital you will notice all the furniture and floors are completely washable. if you visit an adult care home you will find the same thing. All floors are tile or linoleum and all chairs easily wiped down and sanitized. This unfortunately is not a battle you can win.

He does not like wearing disposables so I’m trying to figure out how to get him to use the toilet for BMs. So far he has no trouble urinating. Thanks.

I would say it’s “probably normal”. This is a good time to introduce depends or other pull up disposable brief. (Don’t call them diapers.) I don’t think the elderly dementia sufferers have the same feelings “down there” either due to their brains or their muscles not making the connection when they need to go. When Mom was just starting to decline, it was very hard not to get frustrated/embarrassed, thinking she should be trying harder to control her very occasional incontinence. Now 4 years later on her very good days, she will tell me in advance. On bad days...oops.