Lotsa options, here.
If you can get a gas mask, you'll probably be the only one in there with a gas mask, so you can gas away, sans harm.
You could do your reading online and completely avoid those losers and their precious, loser palace of knowledge.
You could divulge the source of your entertainment to all. Consider it a whispery stand-up set. Most won't complain. Unless the source of your humor is abortions or something else that can polarize the room.
"You know what's funny?" you'll whisper. "How divided we are as a nation." Something like that.
I guess a lot of these are temporary measures, and in your question you ask for a fix. Sadly, it's likely that you're the problem. You should probably go to a psychologist, or better yet, a hyptominust - wait, what are they called? One sec. (Uses internet for knowledge like you should be doing.) Hypnotist? That's it? Anyway. You could use a hypnotist to recover the repressed memories of when you were sex-touched beside the reference materials.
Short Answer: It's totally normal to laugh at times deemed inappropriate by society. You can laugh at funerals for example. If the Barenaked Ladies have taught us anything, it's that.
Other Things the Barenaked Ladies Have Taught Us:
10) Every man becomes a lovesick jerk.
9) Lovers can happen in multiple dangerous times, not just when the original song was written times.
8) Some people put ketchup on their Kraft Dinner.
7) Cocaine can be a secret.
6) Chubby sells.
5) If I call, you will answer.
4) Green dresses are for idiots, you idiot.
3) Everybody wants to fuck Jane.
2) Canada makes weird music.
1) Money buys love.