The bad thing is they don't listen to anyone who is not as successful, or bloated suffering from eating a ton of fruit, they just say get over yourself and go on that treadmill/bike.... they don't think that some of us have jobs and can't spend the day biking/running to get rid of the sugar energy.
But there are other more friendly and less demanding fruitarian sites who say eat until you are satisfied but no more and don't over exercise. Even happy for people to have one cooked meal a day.
I personally believe eating fruit is Paleo as well, and quite believe during paleo times there existed people who wouldn't hunt or can't hunt so were happy with mainly fruit and nuts if available in abundance like in tropical lands. They probably would eat the occasional meat if available to them, but I can't see that it was impossible that some Paleo people ate mainly fruit.