This is a weak, pseudoscientific and pseudophilosophical argument. Relativity doesn’t say all events are happening at once (that would be absurd). It says that time is relative to the observer’s frame of reference (which has real and important ramifications for science and technology). Taking it to the absurd extreme is not only incorrect it is a common proof that an idea is wrong. (Dude accidentally disproves his own argument by making it absurd)