Normal, is sports, fast gas guzzling cars for nobody can take you seriously if you don't have status and huge expensive cars is a great phallic symbol, cop shows, hospital shows, detective shows, sports sport sports sports, talk shows, beer guzzling jocks who were high school heroes and can describe their winning playbook fourty years later, accountants,
D&D is for people who don't fit in society, and only normal people make up society. And Protestant Christians too (not to turn this into a religious rant but you asked) Not nerds and geeks. Nerds and geeks should just stay trapped in the closet and should only come out when a normal person can't understand a computer glitch of some sort.
According to some people.
For the record, I am not normal.
Using the theories by a guy named Jurgen Habermas...
Normal is what is acceptable in the public sphere and requires no further explanation in a discussion. At least in the United States, most normal and acceptable social activities have some kind of public sphere component.
For example: Driving sports cars, playing football, etc.
Watching TV maybe private, but the public component comes with advertising and talking about TV with friends. The same goes with watching movies.
Say, for instance, somebody (say a co-worker whom you're not particularly friends with) asks: "What did you do last weekend?"
You reply: "I played some Xbox, watched the football game, and went to church." No further discussion is required. They might think you're a bit silly for playing Xbox depending on your age, but they'd understand concept of videogames.
However, if you said: "I played Dungeons & Dragons with some friends at my house." Your co-worker would probably ask for further clarification if they've never be directly exposed to the RPG subculture before.
How do you explain it to make it socially acceptable?
Would your reputation be at stake?
The commodification of D&D around when 3.5e was released helped make the hobby more socially acceptable in the public sphere (D&D was repackage and massed produced as "the official" D&D game--the core rules where not touted as "optional" unlike in previous editions). The game, as far as I can tell, in this country has most of its "Satanic" image. 4e has continued this trend by appealing to WoW players. Numerous TV shows have poked fun at the hobby. I think chat rooms like this have helped too, but most people are posting privately and anonymously.
Still, as demonstrated by some of the posts in this thread, this stigma remains.
I, myself, play RPGs and tabletop wargames, but I don't talk about it in the public sphere unless it gets brought up in a discussion or somebody asks me about it. It stinks, but I do think things are getting better in this regard.