It was a local skirmish in the cosmic scheme of things. The Federation is huge and the other races probably couldn't give two figs about a war hundreds of years earlier without the modern tech to detect it. All of the other members of the Federation aren't going to catch that irrational fear, which still doesn't make sense given the time since the war, and would likely not care if a member state wanted to modify itself.
Sure, but that only really matters to the world involved. If they want to prune themselves, what business is it of Earth? And if an individual human from Earth wanted to be modified or modify their kids, what business is it of the world at large?
There are 350 worlds in the Federation. I seriously doubt they're going to ostracize worlds just because Earth and maybe Vulcan want the law to remain. I got the sense that Vulcan only cares about the law as it exists, not that they share Earth's fear.