Why do some Atheists Obsess over Religion?

It has been brought to my attention just how much 'some' Atheists obsess over religion.

I don't know how many times I've seen, read, or heard Atheists get really mad about people believing in God, Allah, Jehovah, or even reincarnation or spiritual philosophy.

Why? If you don't believe it, why insist on making people who do feel inadequate? Why try and undermine someone who does? There are some Atheists who obsess over telling people religion isn't real and how fake their beliefs are.

I don't believe in unicorns, do you know how many times I've thought of Unicorns in my life? Probably a handful of times, and it's usually someone who brings them up. If Randy Rando told me "I believe Unicorns exist in the South Pacific, they have magic rainbow powers that revive Bigfoot Yeti's in the Rocky Mnts if they truly believe in their magic." I wouldn't get mad at them. I don't care

So why get mad if a Christian or Jewish person has beliefs that you think are fairytales? Is it perhaps that you do feel they may be right and have merit, but the anger comes from a place of self doubt?