I suspect a lot of people will say "yes" until the person they're dating or married to has a lot of "opposite sex" friends. LOL!
Most people would rather see their mates hang out with "same sex" friends than with the "opposite sex". The thought of a guy going out to have a drink, bowling, or shooting pool with a (female friend) after work doesn't sit to well with a lot of "girlfriends or wives". Not too many men would be happy if it were the other way around either. This is especially true if the "friend" happens to be an "ex lover".
Honestly I believe men and women can be friends (especially if there is no physical attraction). However it is very common for these "friendships" to fizzle out overtime as one or both them becomes romantically involved with people who may be uneasy with their "friendship".
Sure there are those who will fight their mates in order to keep their "opposite sex" friends but quite a few will simply let the friendship slowly fall by the wayside in order to keep their "significant other" happy.