Explaining the teachings of Khedrup Je, student of Tsongkappa, Shabkar says:

Even non-Buddhists refrain from eating meat.
The sage Sugé said:
All the beasts that you have slain before,
Their blood is like a swamp before your feet.
If that is how you go to higher realms,
Then what is it that makes you sink to hell?

And Netso has said:
The slaughtered sheep, the witnesses of your killing,
Its blood lies in a swamp before your feet.
If that is how you go to higher realms,
Then what is it that makes you sink to hell?

The sage Jawa has said:
The one who eats, the one whose flesh is eaten
See the difference that divides these two!
The one will have his belly full for one short span;
The other has completely lost his life!
Those who understand the fear and pain
Of those who know their final hour has come
Will rather guard the lives of other beings.

Other learned and compassionate no-Buddhist sages agree that to give protection from fear even to a single being is excellent beyond compare. It is unequalled even by the donating of mountains of gold and jewels to thousands of Brahmins, together with gifts of cows and money. Such is the opinion of certain learned and compassionate non-Buddhist sages.

If we earnestly try to do whatever is in harmony with the Buddha's message, regardless of whether it comes from ordinary people or non-Buddhist sources, treating it all as Buddha's doctrine, we will not go wrong.

The Kalachakratantra says that non-Buddhist teachings that are truly excellent should also be respected. And it is said in the Angulimala-sutra that it should be understood that everything that is in harmony with the Buddha's teaching is the Buddha's teaching. All this is the teaching of Khedrup Je.

Shabkar says:

We can see that meat eating is considered wrong by both Buddhists and non-Buddhists alike. One may object and ask why Gunaprabha says in his Vinaya-sutra, and why it is repeated in the great commentary on the same, that if the Shravakas shun meat that is pure in the three ways and can be eaten, they are behaving like Devadatta.
We reply to this by pointing out that Devadatta was constantly jealous of the Buddha. He tried to injure him in many ways, throwing a boulder at him, for example, or setting an elephant on him. In addition, he created a schism in the sangha by saying to those around him, "Look, oh-so-virtuous Gautama eats meat, but we will not eat it, for we would be harming animals otherwise."
In this way, he made a rule that appeared to be more compassionate than the precept of the Buddha. In the same way, if we who are Buddha's disciples abstain from meat because we want to be honoured and are envious of others, trying to appear better than they, we are indeed behaving like Devadatta. But it is quite wrong to compare with Devadatta people who abstain from meat and so on out of genuine compassion, and who do not wish to harm animals directly or indirectly. Such people are like the Buddha himself, or the Bodhisattvas, or the Buddhist practitioners like the Kadampas of old and the compassionate non-Buddhist sages and others, practitioners or ordinary people. If one makes such an error, it follows that one is implying that those who eat meat are behaving like the Buddha. And it would be logical for one to change the text of the Vinaya-sutra to the effect that if the Shravakas eat meat that is allowed because it is pure in the three ways, they are behaving like the Buddha. Many people will no doubt concoct such texts and exegeses - for no other reason than that they want to eat meat.

(Source: FB, p. 89-90)