We all have a right to be angry, and there is much evil in this world deserving of justice. But due to the nature of our society, open calls for violence are not strategic.
Open calls for violence only jeopardize our community, not because they're morally wrong, but because they're illegal. We have to be strategic.
Find another way to release your urge for vengeance. Channel it into something productive. Frame it as a need for self-defense. Let's always remember that we must prioritize the need for a stable community.
Many kinds of advocacy for violence are indeed legal in the US. Specifically if there is no specificity to make it an actionable threat or prohibited language in the vein of inciting a riot.
You can say for instance, "I wish Osbourne would get killed, his music sucks" that's legal, you can't say that you personally would like to do so next Thursday and you really can't say that and add a location you know he'll be that Thursday. What's more sketchy is saying you'd personally like to without specifics such as a date or time, you may not be able to be successfully prosecuted but it is often enough to get an initial warrant for information and a police car roll to your house for them to intimidate you while assessing the threat. And that means you're on their radar and you have failed.
Broad threats are the most legally protected and least likely to get any kind of court approval for more information. Saying "I wish all Green Day fans were rounded up and put in camps" is not anywhere near a real threat or incitement.
One issue I notice with this website is it is incorporated in the US, specifically California. The best legal move would be to base it outside the US, ideally in a country less friendly to US legal and law enforcement requests. If you based it in say Russia or China or any number of places that aren't the US, UK, Australia, NZ, Canada you're a lot safer. Of course the problem is having a person outside the US for that purpose. Hosting it outside the US is also best because it means legally the path for them to get information on a user is so troublesome they'll probably just ignore it. It doesn't mean they won't monitory the board if it comes onto their radar but them having no recourse to grab user IP data would be very comforting to know as an additional safeguard.
If there are multiple people with access to the back-end and/or tools that can grab IP addresses I would suggest any warrant canary have each of them sign their name each month at the bottom of a provision stating the "following persons have not personally received any contact from law enforcement or intelligence or national security organs or agencies regarding the content of this website and its users".