This:

[osmium]

12. The ADL may be, well, biased as one might infer by the data in the chart..

..but that's an ad hominem argument.

Here is their mission statement:

ADL is the world’s leading anti-hate organization. Founded in 1913 in response to an escalating climate of anti-Semitism and bigotry, its timeless mission is to protect the Jewish people and to secure justice and fair treatment for all. Today, ADL continues to fight all forms of hate with the same vigor and passion. A global leader in exposing extremism, delivering anti-bias education, and fighting hate online, ADL is the first call when acts of anti-Semitism occur. ADL’s ultimate goal is a world in which no group or individual suffers from bias, discrimination or hate.

This may be the reason for singling out Islamo-fascists in the chart above. There is a much more granular chart displaying what the ADL classifies as acts by Right-wing extremists on the linked page.

Please note: the data in the chart I linked to is from 1993-2017, so it is not directly comparable, yet instructive in a different manner.

https://www.adl.org/education/resources/reports/dark-constant-rage-25-years-of-right-wing-terrorism-in-united-states

I draw no conclusions as the evidence is incomplete to do so. I used to follow the findings of the ADL much more closely, but something happened in November of 2016, and its impact now takes up most of my available time to do other stuff.