In truth, physical matters like height and size don't matter to Rin in either direction--he doesn't care that Archer is smaller than him, nor does he care that he's larger. He would still, irrespective of size, have approached him in the same manner and with the same ire in his eyes, even if he needed to look up to glare. Despite having several inches on Archer, it's not his height that he lords over his Servant and in the abstract he's not displeased that Archer grounds himself in front of Rin's anger rather than cower back.

The response he receives is not what he wants to hear though. More than that it stuns him enough to make him blink and take a sharp breath in surprise. Archer, in a fairly skillful manner, just turned Rin's sense of his own justified anger at his authority not being respected into an image of him throwing a tantrum like a petulant child. Releasing the breath he'd taken in and held, Rin's jaw sets and his shoulders tense as the anger ripples up his spine once more.

"You--!"

He forces himself to count to five (ten is asking too much) and attempts to reason with himself to give his stubborn new Servant another chance before deploying his final measure to gain control over this partnership. He pushes the fire of his irritation down, a momentary coolness taking its place, though the intensity is far from dampened.

"Don't act like I'm whining over nothing. You don't get to only acknowledge me when it suits you. Servants don't--"

Pausing, something twists in Rin's stomach, an instinctive warning not to finish that sentence. Once, he may have believed that Servants were just puppets and don't have a right to their own will, but that was before he failed Rider so. Instead, he shakes his head, trying to banish the creeping sense of guilt and grief to keep his concentration on the current moment.

"Find your tongue and explain yourself."