A central question of moral epistemology is, or should be: Am I a jerk? Until you figure that one out, you probably ought to be cautious in morally assessing others.
But how to know if you're a jerk? It's not obvious. Some jerks seem aware of their jerkitude, but most seem to lack self-knowledge. So can you rule out the possibility that you're one of those self-ignorant jerks? Maybe a general theory of jerks will help!
I'm inclined to think of the jerk as someone who fails to appropriately respect the individual perspectives of the people around him, treating them as tools or objects to be manipulated, or idiots to be dealt with, rather than as moral and epistemic peers with a variety of potentially valuable perspectives. The characteristic phenomenology of the jerk is "I'm important, and I'm surrounded by idiots!" However, the jerk needn't explicitly think that way, as long as his behavior and reactions fit the mold. Also, the jerk might regard other high-status people as important and regard people with manifestly superior knowledge as non-idiots.
To the jerk, the line of people in the post office is a mass of unimportant fools; it's a felt injustice that he must wait while they bumble around with their requests. To the jerk, the flight attendant is not an individual doing her best in a difficult job, but the most available face of the corporation he berates for trying to force him to hang up his phone. To the jerk, the people waiting to board the train are not a latticework of equals with interesting lives and valuable projects but rather stupid schmoes to be nudged and edged out and cut off. Students and employees are lazy complainers. Low-level staff are people who failed to achieve meaningful careers through their own incompetence who ought to take the scut work and clean up the messes. (If he is in a low-level position, it's a just a rung on the way up or a result of crimes against him.)
Inconveniencing others tends not to register in the jerk's mind. Some academic examples drawn from some of my friends' reports: a professor who schedules his office hours at 7 pm Friday evenings to ensure that students won't come (and who then doesn't always show up himself); a TA who tried to reschedule his section times (after all the undergrads had already signed up and presumably arranged their own schedules accordingly) because they interfered with his napping schedule, and who then, when the staffperson refused to implement this change, met with the department chair to have the staffer reprimanded (fortunately, the chair would have none of it); the professor who harshly penalizes students for typos in their essays but whose syllabus is full of typos.
These examples suggest two derivative features of the jerk: a tendency to exhibit jerkish behavior mostly down the social hierarchy and a lack of self-knowledge of how one will be perceived by others. The first feature follows from the tendency to treat people as objects to be manipulated. Manipulating those with power requires at least a surface-level respect. Since jerkitude is most often displayed down the social ladder, people of high social status often have no idea who the jerks are. It's the secretaries, the students, the waitresses who know, not the CEO. The second feature follows from the limited perspective-taking: If one does not value others' perspectives, there's not likely to be much inclination to climb into their minds to imagine how one will be perceived by them.
In considering whether you yourself are a jerk, you might take comfort in the fact that you have never scheduled your office hours for Friday night or asked 70 people to rearrange their schedules for your nap. But it would be a mistake to comfort oneself so easily. There are many manifestations of jerkitude, and even hard-core jerks are only going to exhibit a sample. The most sophisticated, self-delusional jerks also employ the following clever trick: Find one domain in which one's behavior is exemplary and dwell upon that as proof of one's rectitude. Often, too, the jerk emits an aura of self-serving moral indignation -- partly, perhaps, as an anticipated defense against the potential criticisms of others, and partly due to his failure to think about how others' seemingly immoral actions might be justified from their own point of view.
The opposite of the jerk is the sweetheart or the sweetie. The sweetie is vividly aware of the perspectives of others around him -- seeing them as individual people who merit concern as equals, whose desires and interests and opinions and goals warrant attention and respect. The sweetie offers his place in line to the hurried shopper, spends extra time helping the student in need, calls up an acquaintance with an embarrassed apology after having been unintentionally rude.
Being reluctant to think of other people as jerks is one indicator of being a sweetie: The sweetie charitably sees things from the jerk's point of view! In contrast, the jerk will err toward seeing others as jerks.
We are all of us, no doubt, part jerk and part sweetie. The perfect jerk is a cardboard fiction. We occupy different points in the middle of the jerk-sweetie spectrum, and different contexts will call out the jerk and the sweetie in different people. No way do I think there's going to be a clean sorting.
------------------------------------------------------- I'm accumulating examples of jerkish behavior here. Please add your own! I'm interested both in cases that conform to the theory above that those that don't seem to.