It's one thing to not want it and to be comfortable not wanting it, but viewing it as rude goes way beyond that and is not rational.
I am bothered by random people wanting to talk to me -> Randomly talking to other people would bother them -> Bothering people is rude -> Randomly talking to people is rude.
Hence why the platinum rule is better. Once you know that other people (apparently!) aren't bothered by randomly striking up a conversation, you can adjust your actions accordingly.
No, that rule does not say "it is rude for others to do unto you differently from how you would do unto them"--it's about how you should behave toward others, not a justification for your negative judgment of how others behave toward you.
I agree that the platinum rule is better, but that difference is not the problem here.
If I didn't have that information (and people used the golden rule consistently and weren't just knobheads), then I would be consistently annoyed at people not following the golden rule. As long as my theory of mind doesn't include 'other people generally enjoy random conversations', my perception would be that the golden rule is consistently broken by people striking up random conversations.