Yes that's how this forum works.
Officially you are allowed to accuse anyone of anything, but should provide sufficient proof. In reality people are just saying what they want. You can pick any business that advertises here and start a topic in the service discussion saying it's shit, scam and people should avoid it. I've seen it done by competing businesses like gambling sites, that were using new accounts to start topics meant to discourage people.

On the other hand you have to understand that thoroughly checking each accusation would require a lot of time and effort from staff members. They can't simply delete a thread because you, the business owner, have vouched for it.