A bad experience deserves a negative review otherwise the feedback system will not work.
If you felt uncomfortable for some reason, then a carefully worded feedback can give others the warning without being overly negative. I have not had to give a bad review but have couched some comments about the way some guests push their views too strongly in conversation. I have also got the impression about a potential guest that they were rather loud and opinionated to such an extent that I did not host them. I later met them and confirmed my suspicions.