The threat of violence is unacceptable. Totally.
You do need to know that hearing aids don't always help - they can be physically uncomfortable/painful, they can amplify sounds you don't want, the feeling of having loud noise can be unpleasantly intense, they might not do as good a job as people assume they do and loud sounds such as shouting can be incredibly painful. It can be just as disorienting to have lots of sound as none at all. It's easy to assume that hearing aids fix everything - they don't, and can cause additional problems to boot.
DP would 'forget' I can't hear well on one side and mumble, turn away, cover his mouth and then says 'Oh, nothing, doesn't matter now'. When he's accused me of not listening to him because he's mumbled away in bed when I've got my back to him (so I can have an earphone in to block the constant ssssssssssssssssSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSsssssssssssssssssssssssssssssssssssssssssssssss), I've turned to lipread and hear him, then he's turned away or he's turned the light out before mumbling again, I'm been furious, turned all the lights on, sat bolt upright and said many times I CAN'T FUCKING HEAR YOU. I'm not eligible for a hearing aid. Mainly because the wait time for an audiology appointment is about four years. I might not be eligible by then, either. But deafness is a thing in the family, so I might get them in the end.
If the first I knew of a problem was him shouting at me, he'd be out of the door. Because that would feel like a physical attack. The closeness/in my face, the shock, the physical pain loud noises cause. But he's learned and now puts his hand on my arm and waits for me to turn so I can either hear him or, if there is background noise, lipread. He's also getting good at appearing five foot away (so I don't jump) and signing for Tea? Coffee? Rather than expecting me to hear him from the kitchen. At this rate, we'll be using at least some level of BSL by the time I'm 60. I'll need it, for a start, as there will come a point where I can't make a living with a phone handset turned to maximum (still unable to hear when there's background noise, though - hopefully I'll be able to cope until retirement or we're screwed).