Husbands and their porn habits?

[InbetweenDreams]

I am happily married for many years. Overall, I have a healthy sex life. I have no issue with the fact my husband masterbates occasionally as I also do it myself from time to time. My concern is not so much the use of porn but the type of porn. They seem to only ever watch muscle porn, and for me it is jaring. I don't have a muscled body and I find overly muscled men a little bit of a turn off. The discovery of it often leads me to feel uncomfortable about my appearance and wonder if they'd prefer a more muscular man. If it were any other kink I feel like I'd be able to reciprocate or reenact it, but muscle is something very different in that sense. I am trying to get them to share this side of them, but each time I try to mention the topic it leads to him feeling attacked or shamed. I feel like it is just a side to him that I cannot understand which baffles me. I try to be very open about my sexual side to my spouse. Whilst I do not shout out about the times I may have jacked off, I also will not deny or try to hide it afterwards. With them it is always so secretive. 

Now I understand kinks and porn can be very different to realities, so I wonder if anyone can enlighten me. Is there a way for me to come to terms with the kink and not feel threatened. I do not want to be controlling and furthermore not over analyse the situation.

How do these conversations start that make him feel attacked? Then again he might be apprehensive about sharing that too, kind of like getting caught jerking off when you're a teenager perhaps...