Is he lying about Joss Whedon?

I think he's just naive and doesn't understand that the movie business is filled with assholes who treat actors like props. He's just embarrassing himself with all his whingeing on about it.

Joss is an asshole, but i think he is exaggerating a lot

Ray doesn't like that he doesn't have a bigger role and is using that to make a stink:

"Mr. Fisher recounted disagreements he’d had with the film’s creative team regarding his portrayal of Cyborg, and complained that his suggested script revisions were not adopted. Mr. Hamada explained that creative differences are a normal part of the production process, and that a film’s writer/director ultimately has to be in charge of these matters. "

https://cosmicbook.news/ray-fisher-unhappy-flash-script

That's what this has always been about.

check his filmography, dude hasn't done any acting since Justice League,
he was probably blackballed for being a bitch while filming it & once he realized 2-3 years later without any acting work, he was screwed & decided to be a whiny woman like Gabby Union or Rose Mcgowan

I've heard Whedon can be a dink, but as far as Ray Fisher goes, I'm guessing that he wound up on the cutting room floor a BUNCH and didn't like that. His big break turned into a critically-middling hiccough and he's bitter about it and blaming Whedon.

Now, was Whedon a bully on-set? Was he a jerk? I don't know. But I suspect that Fisher getting cut has as much or more to do with it as anything.

He's trying really hard to be the Colin Kaepernick of Hollywood.

Both of them are wannabe-Muhammad Alis.