Agreed, but that would require acting parties within Twitter to claim they were coerced or forced to act. Knowing who the acting parties were, that's highly unlikely. So I don't think the counter-argument holds much water.
If I understand you correctly, your argument asserts bad faith- that the people involved will lie. So I don't think your counter-counter-argument holds much water, either. And I'm not sure you're even strictly correct- having the employees testify against the argument would hurt, but I could still see Twitter being able to prove they were coerced, or at least try.
You've misunderstood. I don't believe the people who acted felt they were being coerced - I believe they felt they were doing the right thing and were happy to oblige.
Nah, just misunderstood and somewhat continue to misunderstand their point. I don't see how the offered info is relevant to whether this is a 1A violation.
The 1st amendment doesn't come into play unless Twitter is being coerced by the government against their will. There's no legal prohibition against Twitter moderating their platform in a way that also pleases certain people associated with the government.