I suppose this Gemarah went too light as well:
"אמר רבי יוחנן מאי דכתיב ולא קרב זה אל זה כל הלילה (שמות י"ד, 20), בקשו מלאכי השרת לומר שירה, אמר הקב"ה מעשה ידי טובעים בים ואתם אומרים שירה" (תלמוד בבלי, מסכת מגילה י ע"ב. )
I guess the Gemarah just isn't "old school" enough.
I know you have reading comprehension issues so I'll spell it out a little clearer this time.
Jimmy Carter has done quite a lot of damage in his life, he has not endeared himself to the Jewish nation (me included). There is still a big difference between not feeling sympathy for him and rejoicing in a human being's suffering. The former is understandable while the latter comes across as highly immature.
Anyone who knows anything about the Lubavitcher Rebbe's position on Eretz Yisroel knows that there is no one who knew the danger in Carter's policies and opinions than the Rebbe, yet that didn't stop the Rebbe from publicly thanking Carter more than once for the good things he did do (yes there were some of those as well).
Your distortion of the Gemara's words is quite shocking. I guess that what happens when you only learn half a of a whole piece of Gemara.
That piece you quoted is part of larger Gemara quoted in Sanhedrin 39B. There the Gemara EXPLICITLY states that while God himself doesn't rejoice, he makes others (meaning the Jews) rejoice. That's why Moshe Rabeinu and Klal Yisrael rejoiced at Krias Yam Suf and said shira (weren't thinking of that were you?). Even more, the Gemara states that when Achav, a wicked Jewish king, was killed in battle, the Jews REJOICED at his death. It uses that exact word, and quotes a passuk, "with the death of wicked people there is happiness/song/rejoicing". So you see there, your proof is turned on its head by the whole piece in which rejoicing (which you refer to as "immature") is condoned when it comes at the death of wicked people, even wicked Jews.
As for the rebbe, I won't debate on that. I specifically preempted such a challenge by showing how R' Avigdor Miller would act towards Carter, and he's no less qualified than the Rebbe to have an opinion on the matter. I do know that Chabadsters, like all chasidim, tend to mold the Rebbe into the person they want him to be, rather than the person he always was. I don't know if God behavior towards that rasha Carter were as you say it as you want. Either way, the Rebbe isn't the beginning and end to all. Other people have conducted themselves on other ways in regards to American presidents who were Reshaim (all of the recent ones are which eclipsed by Carter).