Some of the language St. Jerome uses towards heretics would make anything we've seen posted by the Dimonds tame by comparison. It's important not to slide into a bitter zeal, but that can't be at the cost of going soft on heresy, since it destroys souls.
There are several problems with this.
1. "Just make sure to avoid bitter zeal?" With the Dimond Brothers, that ship has already sailed. I don't have a problem with St. Athanasius or any other hard-line Trad Catholic (including before the qualifier "Trad" was needed for a Catholic). I'm not after mealy-mouth, nitheness, limp-wristedness, or mincing words. What I WOULD like is the Truth, without any poison mixed in. And dogmatic Home Aloneism ("There is no good Trad group out there to attend Mass with", or the same thing "except these 2 priests") is worse than the Novus Ordo in my opinion.
2. Attacking HERESY and HERETICS is one thing. Attacking all and sundry TRAD/real Catholics? Anathamatizing countless good Catholics, as if you're a Pope with an itchy trigger finger? That's another story. That's why I have NO use for the Dimond Brothers.
Whatever "good" they have done/are doing are being done MUCH BETTER, WITHOUT THE POISON, by countless other priests and bishops (and Trad groups). We don't need the Dimonds. If they were shut down, the world would be a better place.
As for those who "converted" because of the Dimond Brothers, just remember God can bring good out of evil, like the Crucifixion of Christ. Did Pontius Pilate do a good deed for humanity? Of course not.
You show me 10 people who "converted" because of the Dimond Brothers, I'll show you 10 men who would have converted just as well if they had stumbled onto ANOTHER Trad website in their online sleuthing instead, if Dimond Bros had been shut down (as I fervently wish for to this day). And in fact, they'd be better off, since they'd have found the Truth WITHOUT bitter zeal, schism, heresy, error, Home Aloneism, and other garbage mixed in. They'd end up better Trad Catholics if they had clicked on "the next" search result, whatever they would have clicked on if Dimond Bros hadn't been there.