pywren:

“Shat was interviewed on WNEW’s Midday Live,
hosted by Bill Boggs. Asked “What do you think about this trend in fandom,
where Kirk and Spock are more than friends?” Shatner replied: “Well,
they’re gay, what do you think?” He followed that up with “There’s
this sociological thing in the U.S., people are uptight about homosexuality.
The fact that two men are close to each other can invite speculation that they
are more than just friends.”

taken from fanlore

I took this snippet from the original interview, starting at 18:45. The rest is definitely worth watching. Although it was, (sadly) meant as a joke, Shatner continued to talk about how showing emotion and intimacy was still taboo in television at the time.