Joan's anger, just my opinion, stems from shame. She was willing to be a whoreandthe rest of the people in the company were complicit--which puts them on the same level as her, in terms of what they find acceptable for money. Don is the only one with the "virtue" to not sell his principles out for money (Because he doesn't really care about it.)...To come in every day, and know you NEED money, because people depend on you--and to see someone who is immune to the ugly things money does to you, when everyone else doesn't have those scruples? It has to be infuriating--he's the one person that won't get on board. I mean, there are a lot of other things--like Don did blow the IPO for her (Even though he eventually grew the company more). He also doesn't acknowledge people very well. But I think the source of her anger is just that--shame.