In the TURNING OF THE WHEEL DISCOURSE, SN v 421 the Buddha states:
"Monks, these two extremes ought not to be practiced by one who has gone forth from the household life. (What are the two?) There is addiction to indulgence of sense-pleasures, which is hīna, coarse, vulgar, ignoble, and leads to no good; and there is devotion to self-torment, which is painful, ignoble and leads to no good.”
When there is a string of words such as this in the Pali texts, they are understood as being synonyms, or at least carrying overlapping meanings. The point is that at its root, the term Hīnayāna (and its baggage) is not really appropriate to apply to the Theravada, but as I said above, strictly within a Mahayana framework, the attenuated version of the word is certainly appropriate.
In Shantideva's compendium of Mahayana thought, the Sikshasammuccaya, [quoted in Ven Nyanap[onika’s Heart of Buddhist Meditation (not the edited down Boorstein rewrite)] we find quoted from the Mahayana Ayrya-Sagaramati Sutra:
"There is another rule that can serve as the epitome of Mahayana: 'By taking care to avoid stumbling oneself, one will protect all beings.'"
And he quotes from the Bodhisattva-Pratimoksa:
"If, O Sariputra, one wishes to protect others, one should protect oneself."
And here we have the epitome of Mahayana, which is not shunyata, not Buddha-nature or the trikaya doctrine, not the ekayana. It is worth noting the emphasis on individual practice, individual concern in these two Mahayanist texts. Without individual concern, concern for others is not too terribly meaningful. It is worth noting that the above is a reflection of what can be found in a more expansive, earlier Pali texts where we find the Buddha stating:
"'I shall protect myself,' in that way the foundations of mindfulness should be practiced. 'I shall protect others,' in that way the foundations of mindfulness should be practiced. Protecting oneself one protects others; protecting others one protects oneself. And how does one, in protecting oneself, protect others? By the repeated and frequent practice of meditation. And how does one, in protecting others, protect oneself? By patience and forbearance, by a non-violent and harmless life, by compassion and loving kindness." -- S 52,8
We see here –" By patience and forbearance, by a non-violent and harmless life, by compassion and loving kindness” – a very direct concern with the welfare of others. The Foundations of Mindfulness is understood in the Theravada as the core teaching/practice for the cultivation of insight into interdependent, conditioned/conditioning empty nature of one’s experience (dhammas/dharmas), and in light of this I should think such a practitioner would not disagree with Dilgo Khyentse statement in his book, Pure Perception:
When you recognize the void nature, therefore, any notion of there being an ego to dissolve vanishes, and at the same time the energy to bring about the good of others dawns, uncontrived and effortless.
While the Theravada lacks the profound mythic structure of the bodhisattva doctrine as developed by the Mahayanists, it casts lovingkindness and compassion into a far more prosaic, down to earth, practical level of practice:
In the enjoyment of meditation, in the fullness of knowledge and in the strength of mindfulness a person has full enlightenment [sambodhi] and is a shelter for many. - Sn 503
Sambodhi is also used in reference to the Buddha's awakening.
"Cunda, it is impossible that one who is himself sunk in the mire should pull out another who is sunk in the mire. But it is possible, Cunda, that one not sunk in the mire himself should pull out another who is sunk in the mire.
"It is not possible, Cunda, that one who is himself not restrained, not disciplined and not quenched [as to his passions], should make others restrained and disciplined, should make them attain to the full quenching [of passions]. But it is possible, Cunda, that one who is himself restrained, disciplined and fully quenched [as to his passions] should make others restrained and disciplined, should make them attain to the full quenching [of passions]. -- Majjhima Nikaya 8
So, the word hīnayāna is can be a bit of a problem in how it is used. I suppose that the Theravadins could start calling the Mahayana The Grandiose Vehicle, which is amusing, but I think that the while complete agreement is unlikely, there are many points where the Theravada and the Mahayana can meaningfully interact.
So, to answer JMGinPDX, the term hīnayāna has not a thing to do with the Theravada.