Yeah I’m new here, but here are my 2 cents.
#1 AVP is fiction. It’s all make believe.
#2 Given the imagined technological level of the Predators (the ability to travel across interstellar space being the most impressive of them all) being upset that they would have the ability to make a chemical that reacts with the aliens already bizarre body chemistry in such a way that it dissolves them is odd?
They are extremely acidic creatures, so it’s not a huge leap to think they would have a very violent reaction to an equally strong or stronger base.
Acid-Base reactions http://en.wikipedia.org/wiki/Neutralization
There blood is fictional, their origin is fictional, and so is the blue liquid.
Not really the same thing, but the idea reminds me of when salt is put on a slug. It’s not very pretty.