He got screwed over by the IRS a bunch of times, he kinda had legitimate reasons to be pissed off, though hes still a lunatic for deciding burning his house and flying his plane into an IRS building is the best solution.
You can read his suicide note/manifesto on (i think his own website) here, http://http://www.thesmokinggun.com/archive/years/2010/0218102stack1.html
, its seven pages of his life story and run ins with the IRS. The last line is the best, it ends with "well big brother, mr. IRS taxman, lets try something different; take my pound of flesh and sleep well."
On another note, that site has alot of other cool things, like one of the largest collections of celb mug shots. I never knew Tim Allen was arrested in 78 for posession of a large amount of cocaine.