Hi Amnmont
Not being flip, but "everything everyone else has said" from me, plus my thoughts re. your Dad.
Bowel incontinence is very difficult to deal with, whichever end of it you are on. My Mum has just started to lose control in this way, and she feels SO ashamed, SO humiliated, SO disgusted with herself. It is doing her so much damage mentally, and just the thought that she's wearing a pad is enough to reduce her to tears each time she 'discovers' it (she forgets, between times,only to experience all those hurtful, negative emotions all over again.)
Your Dad is obviously going through hell himself, experiencing many of the same emotions, maybe even physical revulsion at the nature of the things he's now having to do
( the first time I cleaned up my Mum up that way, I had a real struggle not to gag & retch. 'They' say the 1st time's the worst!) It's a natural reaction, I believe, regardless of the fact that you may love the patient with all your heart.
I'm not clear if your Dad has any help coming in to help with washing & personal care of your Mum. If he DOESN'T, perhaps you could persuade him to accept help by pointing out that it might enable Mum to stay at home with him for longer (IF that's what you want as a family). And it may be less stressful for her - given that she can't express herself very well now - to have personal care from a paid carer than from a family member.
Forgive me if I'm off beam on this, just my thoughts.