I stumbled upon one such case recently and I kind of wonder how can a person finish his degree in biochemistry and can still say things like "evolution is illogical" and "atheism is illogical"?

You are asking why people believe in a god in the face of scientific evidence. Leaving aside that is not a biological question that is within the remit of this site, more importantly we can't speak for theists nor the reason for an individual's belief in a deity which will be many and varied and very little of which will have anything do with fact or science.