Articles like this are hard to respond to because I agree with pretty much every single thing in it...except for the title.
In cases like the one you describe, the situation is pretty stark: A white guy comes out of nowhere to say he's physically intimidated by a bunch of nerdy academics posing for a picture. He has absolutely no idea how stupid and cowardly he sounds, and then, just to eliminate whatever tiny benefit of the doubt he might have been given, doubles down on his attacks and says, in total seriousness, that black Harvard Law graduates should have their diplomas rescinded because....they looked scary in a pictue?
And what's always insane about this is the persistent subconscious belief that people will rally around him. The total lack of awareness of how childish and pathetic he sounds.
As a solely "stategic" matter, I disagree with your thesis. The "never" part, at least.
There are a lot of reasons we don't have the death penalty for minor crimes, most of them moral. But there are practical reasons too: If people know they'll suffer the same consequences regardless of how bad their behavior is, there's a strong possibility they'll just double down on what they're doing. If you want optimal results, you have to offer a carrot and a stick, and sometimes that means offering forgiveness to minor offenders if they're sincere about reforming.
I see it a lot like a pitched battle in the ancient world. Your army may be winning a decisive victory on the field, but at a certain point, it's wiser to allow the enemy to retreat and surrender instead of fighting to the death of every last man.
Basically, it's more effective if your message to softer, less diehard racists is "We know you've made some mistakes, but we'll forgive you if you just apologize and listen to what we have to say" instead of "We're going to ruin the careers of every single one of you".
That said, guys like this deserve whatever happens to them.