I read an article on CNN that was incredibly sad. A mother who had lost her young son to influenza was allegedly "attacked by anti-vaxxers."  The report said:

Grieving and frightened, just days after her son's death she checked her Facebook page hoping to read messages of comfort from family and friends.

Instead, she found dozens of hateful comments: You're a terrible mother. You killed your child. You deserved what happened to your son. This is all fake – your child doesn't exist…The attacks were from those who oppose vaccination… (source)

Honestly, from the bottom of my heart, it's repugnant. No matter who is doing it, they should be ashamed of themselves. It's on the same level as Westboro Baptist Church members picketing the funerals of soldiers.

The article goes on to say that this is a frequent occurrence, and in fact, planned as a tactic by "anti-vaxxers."