Loud condemnation from the wider community. Contact their employers. Ban them from contributing to projects.
When GamerGate became a thing, every major publication and several major figures in the gaming community all loudly spoke out against the harassment, and many prominent Gamergaters permanently gained reputations as harassers.
Not only do we need this kind of condemnation from leaders within the open-source community, but we need to go farther. We need open-source projects to say "we will not accept any contributions from anyone who participates in harassing GitLab employees", and if they work for a large corporation who's paying them to work on open-source code (e.g. Red Hat, Google), then contact their employers and convince them to cut ties. If you participate in harassment campaigns and sustained personal attacks against private individuals over a policy disagreement, then you should have no place in the community.
You're well within your right to write letters to companies complaining that they employ people who use emojis of rude gestures online. What you don't have the right or ability to do is forbid rude behavior in the culture, rather than on a given platform.
Gitlab isn't in the "open-source community" any more than Oracle is. In fact, Oracle probably contributes more to "Open Source" as a movement and in code than Gitlab. Both are closed-source companies that release part of their works as open.
I can't see tears falling for either of those companies' employees as far as the broader community goes.
Unfortunately the problem has deep roots, and the corporations you mention have a track record of either turning a blind eye to bad behavior when the perpetrator is a popular open-source figure (Google), or actively supporting it because the victims are employed by a competitor (Red Hat).
In general, open-source communities are still stuck in the middle ages from an HR perspective. You can be the victim of terrible behavior, and have no recourse at all, because the project itself has no clear legal requirement to protect you, and none of the corporate sponsors will take responsibility for protecting you in the same way they protect their own employees; even if in practice they are the only ones with the power to do so. The result is a legal limbo where people can get away with terrible behavior. I've seen people get crushed by this, it's kafkaesque.
When GamerGate became a thing, every major publication and several major figures in the gaming community all loudly spoke out against the harassment, and many prominent Gamergaters permanently gained reputations as harassers.
Not only do we need this kind of condemnation from leaders within the open-source community, but we need to go farther. We need open-source projects to say "we will not accept any contributions from anyone who participates in harassing GitLab employees", and if they work for a large corporation who's paying them to work on open-source code (e.g. Red Hat, Google), then contact their employers and convince them to cut ties. If you participate in harassment campaigns and sustained personal attacks against private individuals over a policy disagreement, then you should have no place in the community.