CPU cores have a temperature near 80 °C and then the fan starts to work. Can it be dangerous? (not for Core) I have the same question, but about Core. 

This one I want to ask whether such a temperature is dangerous for other Components, then Core?

I have read some advices to adjust Fan Speed, cause if you use 
MacBook with default configuration it can damage after 3 or more years some of your internal hardware components cause of hot air. The advantage of such a default configuration is
quietly working MacBook.

Are there any information about it?
If its opinion is completely wrong why such Tool as Macs Fan Control are more or less popular?
Intel CPU is designed to work up to 125 C
Your Mac will auto-shut down at 105 C
So the 85 C is almost normal temperature.
Download an install Intel Power gadget made by Intel  to see most acuate information about your CPU
Opinion:
In my opinion the Macs Fan Control is for people who like to play around, your Mac is perfectly capable taking care of it self.