If you can't get a good laugh out of this life, then it ain't worth living. Quite often a sense of humor can lift spirits and lighten the mood, there is nothing wrong with that. No line drawn, as with anything, if you don't like the topic, don't join the conversation.
War, starving children, child molestation, killing, poverty, etc.
I read an article not too long ago about some sicko mother who raped her own 18 month old son and videotaped it to send to her boyfriend - or some such sickshit.
THAT is not funny.
Edit - My bad, the kid is 10 months old. Here's the article: http://news.oneindia.in/2011/09/11/ohio-mother-held-for-raping-infant-son.html
Nothing about child molestation or abuse is funny. At least, I don't find any humor in it. But some do. I've heard jokes on this subject and it disgusted me.
"The LORD will smite thee with the botch of Egypt, and with the emerods, and with the scab, and with the itch, whereof thou canst not be healed." (Deuteronomy 28:27)
"But the hand of the LORD was heavy upon them of Ashdod, and he destroyed them, and smote them with emerods, [even] Ashdod and the coasts thereof" (I Samuel 5:6)
"And it was [so], that, after they had carried it about, the hand of the LORD was against the city with a very great destruction: and he smote the men of the city, both small and great, and they had emerods in their secret parts." (I Samuel 5:9)
If Jews can make their own jokes about Holocaust and Lindy Chamberlain has had to put up with "where's my baby?" jokes for so long, I'd suggest everything has a funny side to someone.
A rabbi once asked his old friend, a priest, "Could you ever be promoted within your Church?"
The priest says, thoughtfully, "Well, I could become a bishop."
The rabbi persists, "And after that?"
With a pause for consideration, the priest replies, "Maybe I could be a cardinal, even."
"And then?"
After thinking for some time, the priest responds, "Someday I may even rise to be the Pope."
But the rabbi is still not satisfied. "And then?"
With an air of incredulity, the priest cries, "What more could I become? God Himself?"
The rabbi says quietly, "One of our boys made it."
Two Jews in Berlin are discussing their plight.
"Terrible," says one. "Persecutions, no rations, discrimination, and quotas. Sometimes I think we would have been better off if we had never been born."
"Sure," says his friend, "but who has that much luck--maybe one in 50,000."
As Hitler's armies faced more and more setbacks, he asked his astrologer, "Am I going to lose the war?"
"Yes," the astrologer said.
"Then, am I going to die?" Hitler asked.
"Yes."
"When am I going to die?"
"On a Jewish holiday."
"But on what holiday?"
"Any day you die will be a Jewish holiday."