No, atheism is not dogmatic.  Theism usally has a dogmatic basis that originates from religious faith in the existence of one or more dogmatic deities.  The "the-" prefix in "theism" means "from deity" and the "-ism" suffix means "doctrine."
The "a-" prefix in "atheism," which means "without," indicates the "absence" of "theism."  (Please also note that anti-theism is the diametrically opposed viewpoint of theism since the "anti-" prefix indicates opposition.)