1. Militantly opposed to religious bullshit(ers) and their prolongation of human conflict and lack of moral concern.
2. The philosophy that irrational organizations of theist doctrine have in their own sacred names raped, pillaged, tortured, burned, hypnotized, vandalized, tyrannized, politicized, suicided, martyred, murdered, infected, rejected, fucked-over and fucked-up the mind/body/spirit/brain/science and all of humanity throughout it's bloody old history of dogma and faith are devastating and ugly.
3. The logical view one attains when his mind has become free to think any taboo ideas.
Antitheism is when you grow up and cut the imaginary friends crap.