If it is your post, use "contact us" (MH suggestions is primarily for features you would like to make the site better).
If it is someone else's post, use the report link next to it. Mods will take a look at it and remove it if it doesn't fall within site guidelines.
another suggestion is go to contact us on bottom of all pages in small print...I would also send a pm to whomever is the CL of the forum you are having issues with and they maybe can help with defusing the situation..
It's my understanding that MedHelp ordinarily won't allow the removal of a post so as
not to disrupt the continuity and flow of the given discussion.
But, if you want to contact them and explain you reasons, go to: Improve MedHelp Suggestions and post this same question there.