To understand much of this scene, you have to look at the previous episode.
In the previous episode, <PERSON> had some tests to see the effect of his chemo and radiation treatments. His doctor wouldn't release the results for four days, but <PERSON> noticed a large white spot on his lung and assumed the worst.
<PERSON> then went into cooking-overdrive, as he believed his life was nearly over and he desperately wanted to raise money. In fact, to quote from the wiki:
Two days of cooking yields 42 pounds of meth that will net them $672,000 each
So they made a serious amount of drugs. Later in the episode, <PERSON>'s fear becomes even clearer:
"I know I can trust you to, uh…" <PERSON> begins.
"Whatever happens, your family will get your share," <PERSON> replies.
Then, at the end of the episode, <PERSON> learns that his cancer is in remission. But rather than reacting with joy, he walks into the bathroom and starts punching the metal tower dispenser with all his might.
This scene wonderfully encapsulates <PERSON>'s state of mind. He is infuriated by his cancer and how it has affected his life. He is infuriated that he can leave so little to his family. He is infuriated by everything. And right when he finds his cancer is in remission, he's still furious as nothing in his life is settled.
When the episode you watched begins (Over) he is recovering from the aftermath of this information. 861
He tells <PERSON> he plans to retire, but two important things happened which change his mind:
1. <PERSON> continues to act the tough-guy and <PERSON> can see how much his son looks up to him.
2. <PERSON> thanks everyone for their support, and toasts <PERSON> and <PERSON> as "heroes".
The combination of these two events has always been a dangerous catalyst for <PERSON>. He wants to be the ideal father figure for his son and is angry that after all he is done, and all he can leave behind, he doesn't get more "respect". This anger isn't at all directed at his son, but at <PERSON> who is his "competitor" in this regard.
Secondly, throughout the series he has a deep and bitter hatred for <PERSON> and <PERSON>. If he had stayed with the business, he would be a billionaire by now - instead he is a drug dealing, cancer riddled secondary school teacher - and he despises it.
Finally, to the scene in question: <PERSON> is angry, he's drinking tequila, and he wants to assert himself. He demands his son drinks because HE is the man of the house. From his drug dealing, he is now used to being in control. He has dealt with powerful and dangerous men - and now <PERSON> is going to influence HIS son, in HIS own house? <PERSON> can't accept that. So he gets into a macho contest with <PERSON>.
As you rightly point out, to any intelligent observer he comes across as callous and childish - but <PERSON> isn't thinking straight, he's drunk and still processing his cancer remission news. 86