If Anger Leads to Hell, Why Do Lord Shiva and Rishis Get Angry?

**"Those under the control of anger have been proclaimed by Bhagavad Gita to be of demoniac nature**, and the ones free from anger are stated to be of divine nature. **Chapter 16, Shloka 21 of Bhagwat Gita** says 'There are three gates leading to the hell of self-destruction: lust, anger, and greed. Therefore, one should give up on these three. ' so why does we see Lord Shiva get angry so many times , even so many Spiritual RishiMunis get angry and give the individual a curse. or is there something i'm missing? I'm just curious , in no way its a hate post . Plz dont downvote me.