The all-too-common "95% of people are idiots" statements. People are smarter than you think. Nationalist grouping - E.g. "You [nation] owe [other nation] for attacking them/us!" Doubly annoying when the two people arguing never even lived during said conflict. The word "whom". When "mature" is used liberally to pass something off as correct.
In any case, what makes atheism the right belief? Is it truly logical to be an atheist instead of a theist? As far as I'm concerenced, any religion is better than no religion.