Watching porn videos is not something unusual. Everybody has at least once watched porn videos. Also masturbating is nothing new. But there is many misunderstanding and misconceptions about masturbation.
Men masturbate no matter what, so it should not matter to you if they are doing it while watching porn or without it. Often, masturbation is a stress reliever for men. Men like things visual but that does not mean that they want to be with the porn stars.
Try watching porn together if you are not okay with your partner’s porn-watching habits. Try and find some female-friendly porn that you both will enjoy.
When you both are on the same page, you will be left with zero insecurities about each other. Also, try and be vocal about your sexual fantasies with your partner. You will not only peep deeper into each other’s like or dislikes but will also connect better.