Texas does have anti-SLAPP laws passed and they are among the strongest in the nation. Unfortunately, the courts have ruled that they cannot be used in federal courts.

Then Linus responded pretty poorly (and ended up stepping down as CEO and is now a chief creative something or other iirc)

Linus didn’t step down in response to this. I don’t remember the exact timelines, but he either stepped down before this, or was in already in the process of transitioning to the new CEO when this happened.

He killed four of his classmates and wounded seven others. 15 years old is old enough to know how terrible the impact of his actions would be. There is certainly more that we as a society could have done to help him with his mental illness, but that does not erase his agency and make him not responsible for his crimes. He has more than earned his punishment.