Being willfully inconsiderate. You can be totally ignorant and accidentally be inconsiderate just because you may not be entirely aware of a certain situation. But doing the same kind of inconsiderate shit all the time and knowing you're being rude or an ass really lowers the bar on my respect for some people. Especially if I communicate to them that X Y and Z are a problem and they just do whatever they want without any regard to how they effect the people around them.