Thing is, Shatner would likely agree with him. He's always been staunchly against stunt casting and cameos without some meaningful purpose for the character's existence. Not entirely sure how old Shatner could legitimately be in this show in the first place, unless he was playing one of Kirk's ancestors.
I read a bit about this after it happened, finding it extremely odd - it looks like Shatner has proxy individuals on-staff controlling the day-to-day operations of his Twitter account, feed and other administrative duties. If he has SnapChat, Insta, FB or other social media outlets, they probably maintain that as well. It's entirely possible these "blocking" actions aren't being cleared by him. Hopefully, with the buzz this particular action has taken, he may take a second look at the criteria by which it occurred. It may have all been just some odd misunderstanding/accident.

No argument there.
Would TrekBBS be considered social media? Maybe in the traditional sense, but these days the definition may have changed to apply to more "modern" variants (Insta, FB, etc.). I'm honestly not sure.