That's what dog whistles do... they make people seem crazy when they question them.
The blood libel myth is well over 1,000 years old. It's one of, if not the oldest antisemitic myth.
Dehumanizing language regarding a people, calling an entire people "Babykillers" is hate speech, period, end stop. Liking the post and then cheering it on is not in itself hate speech, but indicates that you are either highly ignorant of the meaning, or you agree with the sentiment.
Now two Jews have gone out of their way to tell you how hateful it is, its historical context and modern usage.