You can be humorous and friendly at the same time.
Try something like, “as dangerous as crawling across the African Savannah in a sheep costume.”
Here’s a good rule of thumb: Try replacing the subject of the joke with your own group. If you would find the “joke” offensive, don’t use it on anyone else, either.
Example: “About as safe as wearing a “Blue Lives Matter” t-shirt to a ‘mostly peaceful protest’ about the death of George Floyd.”