Yeah, I thought so as well.
If he was so pro-immigration reform that he was re-tweeted by the Obama White House, that doesn't seem likely if he were a Republican.

The claim that Nimoy was a Republican being a natural due to his Vulcan logic is pretty funny, though.

He spoke once at Florida Atlantic University. He came into the auditorium to wild applause and a standing ovation. He waved his hands gesturing for everyone to calm down once he got to the microphone, and said "You people must learn to control your emotions!"

The only other two speakers that stood out to me during my years there were playwright Edward Albee, and Ray Bradbury.