Can a devotee get angry at the Guru?

Yes, a devotee can be angry, no problem. It is very safe to be angry with the Guru. 

Tell me, does anger ask you before it coming? No! You get angry and then later on you feel guilty; I should have not gotten angry. 

So don’t try to justify your anger at that time. You got angry because at that time you were ignorant, never mind, move on!

Changing the system without upsetting those with us

For that you should have skill. 

Truth does not mean rudeness. Often people who think they are just being truthful are very rude. Rudeness blocks communication and can disturb the harmony. 

It also destroys the sense of listening. For anybody to hear you, you should have their ears first for listening. If you block the listening however correct you are it just doesn’t get absorbed. They don’t take it. 

So to buy someone’s ear you should not be rude. And if you are rude you cannot buy someone’s ear. You can be firm but you cannot afford to be rude. And often we don’t know the line between firmness and rudeness. That is the problem.