Only his friend alone can be blamed for the misfortune and the result of his decision. I've got those types of friends before that they've asked me what is bitcoin, stuff about it, and if it's a good investment and I'd told them everything and with a yes. But then later, it seems that they don't believe me and went to invest in altcoins, they just revealed that to me when they lost almost all of their capital to a shitcoin because they thought that I was wrong and they better. Remember that these people are just new to the market, they think that they're better than with those experiences and that's why they gather info and decide to follow their own decisions and not the good advises.
This is the reason on why i dont like on recommending or advising something when it comes to things not only on Bitcoin but also on other stuffs as well as i dont like on getting blamed when things goes shit and wrong.
Just simply tell them about that they should invest on the amount that they could afford to lose and thats all, you should really be trying out to avoid on things because there are people who are really just that good
when they need something from you but if there's none and having no use then they would be starting on having that u-turn against you which do really sucks.
There are also people that don't take advice even if they're listening to us. The reason for that is because they think that know more and better than the person who's giving them advice about the market. No doubt that there are people that are only for the need and will approach the people they know for it. But then, we know that everything happens for a reason and when a friend is like that, fate is just trying to help us avoid these type of people.