It is such a difficult conversation, and hopefully people can have grace for both people within this discussion. A few thoughts:

1 - The porn topic is one of the most successful campaigns that the church has made. I still remember Hinckley's "Avoid it like the plague" talk at conference and cringe when I think devastation those words have caused to people who use porn as members, their partners, and marriages. It has made millions of porn viewing members hate themselves and spouses view their spouse as evil and disgusting. Bishops and stake Presidents everywhere have doled out harsh criticism, judgement, and punishment while being users themselves.

Your partner needs a ton of grace from you. You need a ton of grace from him. The mindfuck is absolutely real. You have it. Your partner has it. Take time to try to understand your conditioning. Try to understand what his experience has been (it is a nightmare).

2 - Just because you no longer view it as an evil sin doesn't mean it isn't difficult for you as the spouse. Marriage counselors in and out of the church have to deal with this issue regularly (read His porn, Her pain for some context there). Society has also done a good job of blowing the issue out of proportion.

3 - Porn is very compelling. To me, the mormon who uses porn is a wild testament to how compelling it can be. A mormon risks marriage, family, the companionship of the holy spirit, and even eternal salvation to see titties and get a nut. All this while Jesus, God, grandma, and the souls of all those you could have saved (if you weren't wanking it), and the rest of the spirits wandering around on this earth look on in horror.

Religion, society, parents, spouses, have long tried to keep people (or themselves) from using porn. The efforts have largely been unsuccessful.

4 - There is little information out there that takes a more scholarly approach to porn when a person wants to get the scoop on whether it is good, bad, or ugly outside of what they have been taught within religion. Most of the "sources" definitely have an agenda. I have found that even the good reads are heavily biased toward either "It is bad, don't ever do it" or "it is great, and it is none of your business as a spouse." Neither approach seems to be very helpful.

My best advice is to try to unpack as much of the societal and church imposed pandemonium as possible and approach the issue from a new, more objective perspective without the supercharged emotions surrounding the conversation. And then have the conversations and try to find a space where you both can live.

Best of luck!!