BoyOnABoat

I had correspondence with a man out of state who made a request along these lines.
He acknowledged upfront that it might come across as rude, and then explained that he had been attacked by a group of Latino men decades ago. He said my appearance reminded him of them, described my look as “scruffy,” and said it was the least sexy a man could be. He then asked that, if I visited, I change how I dress and groom to better suit his comfort.
Setting aside that I’m not even Latino, I found the framing uncomfortable. There’s a difference between a light, reversible request, like specific clothing or grooming for a scene, and asking someone to alter their overall appearance based on a personal association like that.
For me, presentation is intentional and part of how I express myself. I think it’s important that both provider and client can show up feeling genuinely comfortable and attracted to each other as they are. If the baseline attraction isn’t there, it makes more sense to find a better match than to try to reshape someone to fit a preference.

I had correspondence with a man out of state who made a request along these lines.
He acknowledged upfront that it might come across as rude, and then explained that he had been attacked by a group of Latino men decades ago. He said my appearance reminded him of them, described my look as “scruffy,” and said it was the least sexy a man could be. He then asked that, if I visited, I change how I dress and groom to better suit his comfort.
Setting aside that I’m not even Latino, I found the framing uncomfortable. There’s a difference between a light, reversible request, like specific clothing or grooming for a scene, and asking someone to alter their overall appearance based on a personal association like that.
For me, presentation is intentional and part of how I express myself. I think it’s important that both provider and client can show up feeling genuinely comfortable and attracted to each other as they are. If the baseline attraction isn’t there, it makes more sense to find a better match than to try to reshape someone to fit a preference.

"Client refused to send minimal deposit and insisted I pay for my own airfare to go to appointment 🫠"
You don't have to be afraid, just simply be aware of the impact, and ask yourself "will the impact justify this action?"  Some interactions deserve to have poor reviews. In this business a 4 star review is a poor review. 
I am sensing there may be a generational gap here, so let me illustrate more the impact - keeping in the forefront of your mind I have never said 'don't leave bad reviews when warranted'. A online review is modern day version to writing down a notice and sticking it up on a restaurants door for EVERY customer to see before they enter, for the next 5 years (Or maybe a better analogy is placing a stone plaque on the entrance - since they stay there forever.) It is not like a letter to the editor in a newspaper only read by people that week, or chatting with friends about whether you think they would like the movie or not.
It is published FOREVER. Superglued to that provider for eternity like a scarlet letter. Would you feel comfortable posting a note like that to warn people? If yes - write the 4 star review. If no, then don't. 
If a server forgot to add  ketchup in your to go bag with fries, you wouldn't feel like posting the note (I would hope). If the server overcharged your card hundreds of $$$ and then refused to give you a refund, you would leave that note. If the server didn't put ice in your water, you wouldn't feel like posting one, but if they served you a drink in a unwashed glass with cockroaches in it - you would and rightly so. 
It is not an insult, it just has a disproportionate impact than it should. ( Well, actually now I think about it more - you are correct it is an insult, because of the impact.  Maybe that IS a good way to view it. If you want to insult your provider - leave 4 stars. If you don't, don't.)
You are correct that reviews on RM is not a great system. An imperfect system, but it is all we have to work with. For legal reasons the text written on the reviews are only visible to people who are aware that they can do so by using a VPN. All people see is 'this person left me unhappy/unsatisfied', and the inference is 'you will be unhappy too'. 
I guess the other question to ask yourself is - would I hire someone with 4 star review? If you wouldn't, think of that before you leave one. And if you would - just be aware that despite it not bothering you - it will turn many people off from hiring that person again, they will never be able to recover that 5 star rating even if they see 100 more 5 star appointments. If you think that is deserved, by all means go for it. 
If you take this comment as intended Have a nice 5 star day.  If you choose to be offended, have a 4 star one.