If they aren't actively moderating offensive* content: absolutely.
I think he's going to have a REAL tough time convincing a court that Twitter doesn't moderate content given that his justification for starting Parler was Twitter being too aggressive in moderating...
https://www.forbes.com/sites/abrambrown/2020/06/27/parlers-f...
*Offensive probably is the wrong term - content that violates the AWS TOS like calls for violence.