you sound like a bigot women
Of course it's ok to watch porn anytime whether or not you are in a relationship.
When I'm done fucking (before going to bed) I usually have to go jerk off in front of some porn only then I go back to bed with the guy who is usually already sleeping. (cumming just once is probably not enough for me that's why I do that ). I never met a guy who told me it's not okay. And watching porn with your boyfriend can be fun.
I'm not really into "open" relationship but still, watching porn or even jerking off while you are in a relationship is totally okay and normal. I guess you dont understand the difference between a basic physiological need and feelings/love you can have for your BF hence the difference between "fucking" and "making love". Women usually have a hard time understanding that ( not all of them thank god) as their hormonal system is not made to be constantly ready to procreate like ours.
If one day I met a guy telling me I can't watch porn/jerk off when I'm not with him.. well I'm out
so be careful as I'm pretty sure I'm not the only guy thinking that way ( or the guy will just lie to you..and lies are known to be healthy in a relationship