Even if you believe this Roper guy doesn't have an axe to grind and is genuine, the underlying theme of the responses to his dive shop vitriol seems to be that Robert's Grove is a fine place to stay. Even Mr. Roper doesn't try to imply otherwise.
If you like RG, why not book the accommodations but wait until you get to Placencia before you select your dive shop? If you don't like what you see at the RG dive shop I am sure that any other dive shop will pick you up from the dock at RG.
I do find it suspicious that Mr. Roper claims that he designed and ran the RG dive shop for 2 years and that in his opinion it is incredibly unsafe. If I were he I wouldn't impart this information to my next potenial employer......