1) a priest who was not conditionally ordained (he had refused conditional ordination) being allowed to offer Mass at SSPX chapels,
2) acceptance of Novus Ordo marriage annulments,
3) imposition of the 1962 Missal (these priests merely opposed being forced to use the 1962 Missal), and
4) suppression of the freedom to question the legitimacy of the V2 papal claimants.
From an outsider looking in, I think point 1 is a legitimate, grave concern. We see the slippery slope has led the new-sspx to use "bishop" Huonder.
Point 2 is just impossible to fix, practically speaking. There's millions of people with fake annulments and only God knows the answer. The good news is, most of these people are not Trads, so (hindsight being 20/20), these people never came to Tradition and priests didn't have to mess with them. But, at the time, I'm sure this issue needed to be debated.
Point 3 is just making a mountain out of a molehill. Nothing wrong with the 62 missal, as many have pointed out. I think this was a scrupulous addition to the list.
Point 4 sounds good, but I'm not sure there was actual suppression of freedom. I wasn't there; don't know. But it's not a major doctrinal issue.
I'm sure the "nine" had good intentions, but with hindsight, we now see that almost half of these men became bishops and the other half were very active in building Tradition (and still are). I just think these guys were independent types, and wanted to do their own thing. Nothing wrong with this, and it probably saved the sspx a lot of headaches by them leaving. Too many cooks in the kitchen are bad, as they say.
The only negative out of this division was the lack of "moving on" and forgiveness, by both sides. The growth that both groups experienced was good, and helped Tradition in different ways. The long-term bickering and competition between groups is not good.