It's called a fallacy of relative privation, or "whataboutism", also known as the starving kids in Africa defense. We just had a Critical Miss strip about it due to Jontron attempting to use it as a defense against people criticizing him.
It was dumb then, it's dumb now, and it always will be dumb. It falls into the same category as basically telling people to shut up because they are talking about or caring about something that that person doesn't care about. It's a dumb argument because it can be applied to pretty much anything that can't be called a crisis or "serious" issue, and the person making the argument always seems to think they are the sole arbiter of what issues are important enough to care about.
It's also an issue of presumption, it's an argument that assumes the opponents position on issues unrelated to the current topic and then casts moral aspirations on anyone that dares to defy the invokers moral standards. Its an issue that also tends to warp the concept of how much people are actually caring about an issue by trying to frame the less important issue as much larger than it actually is. I.E. people will care about and post sympathies over Robin Williams death, but far FAR more cash, volunteer hours, attention, care, and effort will go into the Gaza crisis because despite what people on the internet claim, the vast majority of people do indeed realize that the Gaza situation is the bigger crisis, and react accordingly.
I see this argument in regards to everything, pretty much any complaint that isn't the absolute worst atrocity in human history will receive an argument of "whataboutism" at some point, I've even seen it applied to murders, rapes, and kidnappings, usually with some yahoo commenting about why the news is commenting on some individual tragedy whilst wars and massacres are going on.
It's a particular pet peeve argument of mine because of just how presumptuous, inane, and useless it is.
It never works, and anyone with more than 2 braincells to rub together can pretty much see through the ruse and realize the person making the argument isn't actually interested in getting people to care about the bigger issues, they either just want people to shut up about the current topic, or they are trying to gain a non-existent moral high ground for their own self-gratification.