No, it really isn’t.
I have signed more of these I can count, and reviewed more agreements than I can remember, including for organizations as big as the WMF, and I guarantee you they all say in them that they can terminate immediately if they feel your use of the service may cause harm to AWS. Being associated with a site that hosted a seditious assault on the government of the USA, while simultaneously refusing to ban users walking around using the hashtag #6mwe (6 million wasn’t enough) is more than enough grounds to say the risk of boycott or other harm in-market was too great. IANAL, but IMHO there is zero chance Amazon’s legal department didn’t make a determination along these lines prior to the action being taken.
Parler doesn’t have a leg to stand on here.
In fact, took me all of a minute to find that clause. I recognized it immediately, every AUP has one of these:
6.1 Generally. We may suspend your or any End User’s right to access or use any portion or all of the Service Offerings immediately upon notice to you if we determine:
(a) your or an End User’s use of the Service Offerings (i) poses a security risk to the Service Offerings or any third party, (ii) could adversely impact our systems, the Service Offerings or the systems or Content of any other AWS customer, (iii) could subject us, our affiliates, or any third party to liability, or (iv) could be fraudulent;
