I think you cared to have an open mind about it, you would find that in practice, libertarians will step up and help those in need just as much any anybody else would. The extent to which people will do so is more dependent on their own moral compass and ability to help others than by their political ideology.

What libertarians are against is coercion and force. They don't want to be forced to do what somebody else thinks is morally proper, in most cases for yet another person. That way lies tyranny.

The concept of selfishness in the libertarian sense is "put your own oxygen mask on first before helping others".

Most libertarians are pretty generous givers in terms of both charity, emotional support, helping hands and community. They just dislike having a gun to their heads to be that way.