Okay, take this as my opinion because that's all it is - my opinion.
I hear so many guys complaining about controlling partners, etc especially when it comes to things like Facebook and such. Well, it's pretty normal in a relationship for a partner to be curious about your activites online, who is interacting with you, and what the intent is. It really doesn't mean he doesn't trust you. I know you might say, "If he trusted me, then I could do anything and he wouldn't worry!" but even though people like to say that, it's not completely true. Yes, generally partners should trust one another. However, the online world is a little different. I don't have Facebook and even if I did, I wouldn't "Friend" my partner. In RL, you aren't with your partner 24/7 and don't see every interaction he has with other people. When you are together, it's very easy to tell in RL what people's intentions are, their subtle nuances are, and see how harmless everything is (usually). Online interactions are missing so many cues and it is by nature a bit secretive even if it's not intended that way. Also, boundaries seem to get blurred online. People are more aggressive, flirt more, and generally go past boundaries they would not in RL. This is one reason I stay out of social media.
It's so easy to mis-interpret things online. Even I have a hard time telling what people are saying to ME, let alone an interaction with someone else.
Keep in mind, that in human history of relationships, this "online" element is extremely new. It makes a lot of people really nervous. So I think it's a dialogue every couple should have. If you are a person who has an online presence, you need to make it clear in the beginning (you know, when couples are talking about all the other dos and don'ts in a relationship). It has to be a boundary you set like any other.
I don't think guys who dislike online socialization are controlling necessarily, unless they are telling you to delete your account (especially if they have one themselves!), but they are just very nervous. I don't think people know how to deal with this quite yet. I know that I have had 2 partners cheat on me with people online. I myself don't hang around much online (except on GS because I am house bound mostly nowdays) and probably would do best with a partner with a similar lifestyle as my own. But I've done enough introspection to know this about myself and would NEVER date someone and then tell them what to do!
I've also noticed several friends who claim their interaction on FB is minimal and harmless, but it's really quite the opposite. It kind of goes with the weak boundaries issue I mentioned above.
OP, if this is something that makes you unhappy, then I'd make it clear in the beginning of a relationship that your social media is private and your partner should respect that. Yes, your partner should have respected it anyways, but I think he could have been trying but his insecurity got the better of him. I'm sorry for that.