Yeah, how dare he keep an obligation to the charitable organization he agreed to help! What a jerk!
For crying out loud, people, Shatner wasn't even in the same country. It's not like he decided to ditch the funeral so he could go golfing.
I think that this was only true back in the TOS days, where they had a genuine rivalry. By the time they got to the movies, they grew much closer due to shared life experiences. Watch Shatner's film
Mind Meld and you'll realize how close they truly were. It's about 60-90 minutes of Shatner and Nimoy in conversation, talking about some very delicate subjects (including Nimoy's alcoholism and the death of Shatner's wife Nerine). Do you think that Nimoy would have agreed to do such an interview at all if he & Shatner hadn't been close? And at the end of the conversation, they hug each other as Nimoy quietly tells Shatner, "You're my best friend." It's obviously genuine.
And I don't know about you, but I tease and playfully insult my closest friends all the time. It's one of the marks of true closeness that you can say things like that to your friends and they won't take offense but just laugh. If I genuinely, truly, don't like someone, I generally don't bother engaging them in
any way.
I think you're misreading their vibe depending upon the vintage of the interviews. By the 80s/90s, they were thick as thieves.