>> To many leftists it appears that all mass shooters are by definition white supremacists and rightwingnuts.
With the exception, the Leftists are simply wrong. On the other hand, Islam is in fact perpetrating atrocities on a regular basis... which includes using civilian aircraft as a weapon.
That many mass murders are committed by Islamists does not mean any particular mass murder is.
Think of it as profiling. Islamists fit the profile for mass murderers. But the perpetrator of any given crime may or may not fit the profile.