I understand your frustration but secret shoppers are important to any business even if that business happens to be renting out a place you own.
Your guests can pay up to several hundreds of dollars worth of fees for the Airbnb service so why would they not want to make sure your reviews aren’t skewed, your service and property are what they say they are, and the service you are providing is worth what people are paying?
If all of those things are truly what you say they are then respond in kindness, address the issues, and don’t publicly complain about a guest.
Those who have done nothing wrong do not rant or publicly shame someone, they also do not over explain things.
If you want to be praised in public, then punish in private. Always try to remember these people are making you money they are your guests, some will say nice things someone will not - even if they are not shoppers, deal with it.