I probably could have communicated better, but there is simply no way they can justify giving me such a low grade.

There's probably something we can dig into here. How could you have communicated better? Group work is all about communication, so it's a bit problem if this is an issue.

In my experience, it's very unusual for an entire group of students to trash another student. I've actually never seen it happen without some sort of valid justification, even if they are being ruthlessly harsh.

I'd suggest trying to learn from this experience, because the purpose of low grades isn't to punish you, it's to realize that you've failed in some area and need to improve. What did you do that caused your entire group to trash you? How can you not do that next time?