Aite means the Opponent in Shoubu.
However the word Aite has a deeper Meaning in Sumou. Literally it means The Reciprocal Party and this is its hidden Meaning.
Your Aite is not only your Opponent, but your Partner. He is the one who is giving you a chance to Improve Yourself, to make yourself a better man, to overcome your weakness, by reaching deep into yourself and finding Power enough to overcome him by pure force, no tricks.
This is why it's essential to Respect your Aite in Sumou. Since he is not your Adversary, but a Helper giving you a hand to overcome your own Weakness.
For this it's essential that the Respect for your Aite govern your behavior on the Dohyou. This is why you must control your Emotions and not project any.
Since if you overcome your Aite, he has helped you to overcome yourself and you must not display happiness at Winning, since that way you are being disrespectful to him.
Sorrow in Losing is the same thing, if you have lost that means you have learned that you must exert yourself more and displaying loss shows remorse at how strong your Aite is. Again - disrespect.
In Sumou Respect for your Aite plays an integral part of the process of you growing and making yourself more powerful, a better man.