Better try to stay away from personal accusations, he's just trying to keep this a safe place. 

To kick-off your project i would recommend to do 2 things:

1. Give away vouch copies to highly trusted members at no cost.

This requires some investment from your side.
Open a thread especially for that purpose. You should set up the Bitmex account and VPS by yourself.
Fund the Bitmex account by yourself. Create the keys (ofc without withdraw permission) and give the login credentials to the tester.
He then can monitor and report the activities. (of course this requires some trust, but this is the risk you should take)

2. Open a reputation thread.

Let customers share their experience with you and the bot.
This will clarify your legitimacy.