The word holocaust, as in "The Holocaust," should, in my opinion, be reserved exclusively for the mass slaughter of Jewish people and various minorities by the Nazis. Using it in other contexts, again in my opinion, devalues the dreadful impact of what the Nazis did, and that is just not right. There are plenty of alternative words available. I know that the word has other senses, many of which go back a long way, but in my view it's invidious to try to hang on to them when we simply don't have to. Most of us now regard people who insist on hanging on to "gay" to mean happy/jolly/merry as somewhat odd and a bit old hat. We can get very cross when we feel that someone has usurped one of our sacred words, but that's language for you, and, as I say, it isn't hard to find alternative ways of fully expressing what we want to say.