I'm looking at the unions that were the strongest, the most powerful, and the most influential. The IWW was never particularly strong after WWI, and that was at the peak of their membership. AFL- and CIO-affiliated unions were the strongest - and, more importantly, remain so to this day.
It's funny you mention the porters' union - they were the first to receive recognition by the AFL. Why is that unusual? Well, they were special not because they were a union that represented black members, but because they were the first union of black members that the AFL didn't deny membership to based on race, after decades of explicitly prohibiting black unions from joining their federation. (Even after that, they refused to recognize most unions that accepted black or Japanese workers as members).
> I'd even go so far as to say that actually your comment is the revisionist one.
No, it's not "revisionist" to point out counterexamples to OP's claim, especially when those counterexamples include the largest group of unions for the last 100 years.
Yes, sometimes it's convenient for labor unions to leverage rhetoric that flirts with socialism or communism, but in reality, their source of power is dependent on both capitalism and class hierarchy, which is why the largest and most influential ones have fought so hard to preserve it.