Quote:
Originally Posted by
Shaded Dogfood 
The irony is that Don pretty much forged his own life, and we're not talking anvils.
I'm not sure it's the same. This was about loyalty and character. Lane put the company in jeopardy, lied to the partnership about very serious financial matters, and embezzled $8000 when he could've just asked someone for a personal loan and Don surely would've given it to him.
As the partner meeting at the beginning of this episode made clear, Lane is the only person among the partners who has any sense of how financial matters should be handled. If he's using that power to take advantage of the company? That is a serious, unforgivable breach of trust.
And when Don confronted him about it, he didn't confess. He doubled down on the lie, clumsily and obviously. And then that whole conversation after he did admit it, Lane was basically saying, "You got rich off the sale to PPL; I've gotten nothing from SCDP. I deserved that money. It was
mine." It wasn't even really the company's money. It was part of a significant credit extension from the bank that he lied to the partners about to justify unnecessary bonuses. That is not someone you can keep around.
Don is huge on loyalty and trust. He wanted to fire Pete over talking creative after hours with Bethlehem Steel. And he wanted to save Freddy when they fired him in Season 2 because of his loyalty, despite his highly irresponsible behavior.