Well, there's something to be said for lightening up, and unless assaulted, we choose to be offended. I suppose, similarly, most really can't stand Jerry nor find his behavior humorous; he's such a jerk to Tom.
The art of parody can be low or high brow. I suppose there is some low brow parody I do not appreciate (e.g. Jim Carrey's Fire Marshal Bill Burns I find disturbing), but BOFH hits too close to home for me to criticize (beyond literary). Some users can be demanding, needy, ungrateful pieces of work, and fantasizing about retaliation without consequences relieves pressure.
Contrast BOFH to dissident heating engineer Harry Tuttle, not opposites, but somewhat complimentary. BOFH is probably more believable, but Harry wins the absurdity contest. Also compare both to Dr. Gregory House and the characters on Seinfeld. I will not explain why we sometimes like horrible people, but I think it is intersting that Tuttle stands out conspicuously gallant and heroic among them.
We even like antiheroes in work that is not parody, such as Clint Eastwood's unnamed characters, Han Solo, Michael Corleone and Rambo. There are other crossovers like BOFH, such as Captain Jack Sparrow, a character that is similarly both a parody and an antihero, or Alex DeLarge, a satiric antihero. Also notable is Mr. Robot's Elliot Alderson, perhaps a closely-related descendent of BOFH.