Earlier quoted context omitted.
Linus regularly and repeatedly was cruel to people when he perceived they made mistakes. Examples of his behavior are easy to find, and widely cited in any discussion on HN about it.
No, he wasn't cruel to people. If someone makes a mistake and one reacts to that with strong language is not cruel. It's actually love. People make stupid mistakes. Making them and everyone else understand that certain stuff is not acceptable is important. Was it absolutely necessary or optimal to react that strongly? No. But not cruel.
Insulting people is necessarily cruel. It is done to make the one saying the insult feel better at the expense of the one insulted. And insulting people is not necessary when correcting them.