The ACLU does debate and reflect, but they _have_ visibly changed in the wake of Charlottesville. The ACLU writing a rebuttal article listing their defenses of right-wing speech since 2017 doesn't really fix that image.
There are multiple causes: even though it is not the ACLU's fault for the murder at the Charlottesville rally, its public image took a beating. Combine that with the massive influx of new supporters and new money in 2017, in support of the ACLU directly challenging Trump, it now has a lot more partisan supporters than it used to. Donations have tripled. Even if all previous supporters were right-partisan (which would be unlikely), the sudden addition of a bloc of left-partisan supporters, double the size of your previous supporter base, could sway your organisation.
From the NY Times article:
> But in interviews, several younger lawyers suggested a toll taken. Their generational cohort, they said, placed less value on free speech, making it uncomfortable for them to express views internally that diverged from progressive orthodoxy.
> “A dogmatism descends sometimes” inside the A.C.L.U., noted Alejandro Agustin Ortiz, a lawyer with the racial justice project. “You hesitate before you question a belief that is ascendant among your peer group.”
> Some argued for carefully vetting hires. “I never do a job interview without raising Skokie/Charlottesville and asking if they are comfortable with that history,” said a lawyer who asked not to be named because of the fear of inflaming colleagues. “Not many colleagues agree. It’s about the cause.”
It seems there is both an "old guard" and "new guard" within the ACLU, only time will tell if they retain full commitment to defending free speech.