I recently found out a lifelong friend of mine is a nazi (he uses all the nazi sites like 4chan and reddit etc)
What should i do?
Dont listen to this guy, thats literally 1head take. Do what you feel is right. My advice would be distance yourself immediately, depending on how serious/long he's been involved with this ideology. If he's open to your point of view, explain why you can not associate yourself with him anymore. Dont feel bad for distancing yourself tho. This isnt a case of unfriending someone due to their simple political preferences, this is 1000x more extreme.