Attacking your enemy when they are weak only really applies when your enemy is equal or stronger than you. If Mike Tyson wanted to fight a random person on the street, he wouldn't be worried about whether the guy was feeling strong or weak.
As demonstrated on the thousands of posts here, China is significantly more powerful than India.
All countries have hyper nationalists - I think this fellow is one of them.
I generally agree with the strategy Chinese policy makers have had on India. Beat them geopolitically, support their enemies and turn their friends into Chinese allies. Respond to any Indian military incursions with overwhelming force and a gradual push of the LAC towards India.