I think it's because most fans know the kind of man Wally would eventually become and he had good will from the JLU show so they are willing to overlook his flaws during the early part of the run.
That's been the case for me and several other fans who got into the character during the early 00's. We got into the character thanks to JLU and thanks to the comics being published at the time we knew he becomes a better person eventually.
You also have to factor in his abusive father, his overly dotting mother and the fact that his largely cut off from the people who could bring out the best in him; his mentor was recently deceased, his aunt was missing and the Titans have their own interpersonal drama. Not to mention the mind fucking by Raven probably warped his view on women. He was a jerk but there were reasons why he was that way and he eventually out grew it.