I don’t see why the attitude of the reporting user should be a factor in determining the priority of the bug they are reporting. Surely the severity of the bug, and how many people are likely to be affected are the relevant factors. Sure, if the issue is not well explained, hard to pin down, or might otherwise require cooperation from the user, you have to weigh that into your consideration. However, many users do get surprisingly cooperative once you show them that you actually care about fixing the issue they are reporting; many users are used to being ignored, and might start out having a bad attitude merely by habit.