"We fully support criminal and civil liability for those who abuse and harass others."
That's not sufficient. These are extremely slow mechanisms, when they work at all. The harassed individual can suffer for years, and the EFF isn't rushing out to aid them. As their post says, "law enforcement and legislators have failed".
The Internet is different from the physical world. It's much easier for people to cross legal jurisdictions and hide from law enforcement. Law enforcement and legislators haven't merely failed. They will continue to fail for a long time, during which there are real consequences to human beings.
The Internet is going to have to develop its own ways of dealing with people who use it to harm others. The EFF could help lead that. But they haven't yet, and so others are going to take action when they feel it's appropriate. They'll take the EFF's injunction to "resist the temptation to step in" as being worth the paper it's written on.