I didn't take the DU OP literally, and didn't realize Elijah Cummings actually had died unto going to another discussion site (it's ~5:40AM here, and my coffee maker just finished, so I haven't been rooting around the 'net much yet). With that intro ...
There are idiots and assholes across the political spectrum. If DUpipo want to see their assholes in action they should just browse their own threads about the deaths of G. H. W. Bush, Gerald Ford, Ronald Reagan, and Bob Hope. DUpipo have less than zero credibility in criticizing anyone rejoicing at the death of Cummings.
What would I do? Well, at the time Ted Kennedy died I was a Mod on The Annoyed Army, a small, now defunct, conservative discussion site. As soon as I learned Teddy had died I posted about it, emphasizing that it was a time to sympathize with his family, etc.. And that's what happened. Had I and other Mods not posted along those lines, would there have been asshole-grade Snoopy-dancing? I can't say. We/I just did what we did to keep things decent; the multitude of DU threads I referenced above show what DUpipo and DU-Mods are.
IMO, Cummings harmed the US, but eternal matters are infinitely above my pay grade. Age 68 is fairly young, and his death may have been unexpected. But even if it was expected his family are in need of comfort, which I hope they find.