If you are not aware, Shatner doesn't like Takei.
Takei married his husband in 2008 and Shatner became enraged when
he claimed he wasn’t invited. He ranted against Takei in an
online interview. [...]
Shatner called Takei’s wedding a publicity stunt and hypothesized
that their feud stemmed from Takei’s unwillingness to playing
second fiddle to Shatner on “Star Trek.”
It seems to be mostly based on petty, even comical stuff like this. This may sound paradoxical, but as someone who always had a lot of respect for both of them, this is disappointing and a bit of a relief at the same time.Which, of course, humorously confirms all of the casts' characterizations of him as a selfish egomaniac in a wig and a girdle. I think that Shatner is aware of this (within the past 20 years, not at the time) and plays into it for the humor value and a media bump if he's currently selling something. He's always selling something.