Urm... Lester has finally started getting what he wants out of life - he's shed his horrible job and walked away with money. But at home the situation is just the same - he can't even get the asparagus passed to him?? It's symbolic of another obstacle he has to overcome to achieve freedom - his home life? (Man, that sounds pretentious!)

And the only way of getting that freedom and getting what he wants and what he feels he deserves, is to go get it himself - no one is gonna give it to him. He has to take charge of his own life. And when he does get it - the freedom to do what he wants/asparagus - he takes it too far and sabotages it.

In the same vein, I always thought the asparagus was a symbol of his powerlessness -- he can not be heard even by his own family -- and when he flings it against the wall, he is saying, "That's it. I am claiming my power." Which is what he does, getting in touch with his core essence, unfortunately almost exclusively his selfish desires (personified most notably by his fantasies re Angela). It's only when he sees her for who she is -- a scared little virgin -- which causes him to get in touch with his kindness and genuine paternal instincts that he takes a first step toward possible wholeness, but of course by then it's too late. Blam! End of story. Hence the tragic aspect of the satire.