While protein does stimulate insulin secretion, I would not say that it “spikes” it.
We need a certain amount of insulin in our blood, or we’ll starve to death (remember the fate of Type I diabetics before insulin was discovered), so stimulating insulin in moderation is a good thing. Even fat stimulates insulin secretion a little bit, although hardly at all, when compared to carbohydrate (or even protein).
Carbohydrate, now, that can spike insulin, if eaten in quantity. And even in the small quantites a ketonian eats, it does stimulate insulin somewhat, and the effect is twice as strong as that of the same amount of protein.