What should you do when others speak against the teachings of the Buddha?

You should defend the dharma and protect the precious teachings of the Buddhas like a ferocious tigress defends her cubs. When you see evil ideas being expounded that will harm the good roots of others, do not be passive and allow someone to believe that which is harmful to them. It is true that you should ignore what others say to malign you, but not what they might say to defame the dharma.

H.H. Dorje Chang Buddha III has told us that “The wrongs of others are my wrongs. To regard others and yourself as one is great compassion. A true cultivator regards the mistakes of others as his own mistakes. Do not talk about the wrongs of others. Do not make known your  meritorious deeds. Speaking of your meritorious deeds shows your dark karma.”

Erroneous View #8:  ACKNOWLEDGING THE EXISTENCE OF EVIL DOCTRINES, BUT NOT STOPING THE EVIL TEACHINGS OR ALERTING LIVING BEINGS
When those with this view see someone spreading heretical ideas that harm sentient beings, they just think of cultivating themselves and do not care about others. They think, “Another person’s mistake is equal to my mistake. To view everyone as one entity is to have great compassion. I will not tell others about this. I will not do that. I will just concentrate on cultivating myself.” Such a perspective is wrong. You must do all you can to stop heretical ideas. You should tell those people who heard such ideas, “What you heard are heretical ideas that go against the teachings of the sutras. Our master H.H. Dorje Chang Buddha III does not utter such ideas.” You should remember one thing. Whenever you see someone spreading heretical ideas, you should notify living beings of this so that they understand. Do not let his heretical ideas continue to harm more living beings. However, you must bear in mind that if his petty words are directed at and harm you, then you should think, “Another person’s mistake is equal to my mistake. To view everyone as one entity is to have great compassion.” You should endure such insult quietly and should not tell others about it.