In the sense that are a tiny subset of a much larger group? Well, sure I agree.
Or in the sense that "white supremacist" besmirches white people the way that "Radical Islamist" besmirches Islam? Ok, I'm not against referring to them just as "racists" or the groups by their respective names (Neo-Nazis, KKK, and so on).
In either case, your comparison between Trump and Obama doesn't hold up.
> "Trump has not denounced white supremacist terrorism" is the equivalent to "Obama has not denounced radical Islamic terrorism".
Obama DID denounce "radical Islamic terrorism," though he did not use that exact term, for the reasons described above. For example, Obama said the following regarding the San Bernardino shooters:
> So far, we have no evidence that the killers were directed by a terrorist organization overseas, or that they were part of a broader conspiracy here at home. But it is clear that the two of them had gone down the dark path of radicalization, embracing a perverted interpretation of Islam that calls for war against America and the West. They had stockpiled assault weapons, ammunition, and pipe bombs. So this was an act of terrorism, designed to kill innocent people.
Trump denounced the racists in Charlottesville on Monday, but his statement Saturday did not.
It just vaguely criticized "hatred and bigotry," without referencing the fact that in this case the hatred and bigotry was that of Neo-Nazis, KKK, and other racist groups. To me, his statement sounded like he thought the counter-protesters were equally guilty of "hatred and bigotry", and I think many other people felt the same.
If Trump's statement Saturday had been like the one on Monday, there would have been no controversy.