The ironic part of homophobia is that one factor that helps create it is due to one unintended consequence. It's a consequence of a very famous and essential ethical and moral idea. That idea, expressed somewhat hypothetically, is called the Golden Rule:

"Do unto others as you would have them do unto you."

The problem comes with the idea implied in that one. It is the unspoken iron rule of reciprocation:

"If someone does unto you, you must do it unto them."

It is the basis for the ancient lex talonis: an eye for an eye and a tooth for a tooth. Damage my eye and I damage yours. Tit for tat. Unlike the Golden Rule, this is in a negative form and is not a bit hypothetical.

We see the Golden Rule's corollary expressed in all forms of gift-giving that implies gift exchange. The strength of the idea of exchange can be seen in the fact that children accept holiday and birthday gifts with no obligation to reciprocate--up to a that undefined age when they are expected to begin giving gifts. Another exception proves the rule: the traditional one-sidedness of gifts given by men to women during courtship.

This reciprocal obligation based on the Golden Rule's corollary includes the buying of drinks in a bar. If I accept a drink from you, I come under an obligation to buy at least one drink for you. I avoid that obligation by not accepting gift drinks. On the other hand, by not accepting, I may cause other problems if declining is interpreted as a refusal and, in fact, a personal insult.

So, it's fair to assume that an important factor in violent homophobia is the belief, somewhat unconscious and rarely expressed, even to oneself, that if he offers, I should offer. If he gives me pleasure I should give him pleasure. Or, if he desires me sexually, I should desire him.

The iron rule of reciprocal action says in each case: Yes, you must. If he does to you, you must do to him. Pleasure for pleasure.

It's interesting that the choice of declining a homosexual offer, by itself, is not set up societally to be interpretable as a personal insult to the person being refused.

In fact, the reverse is true. To a heterosexual, a man offering oral sex is insulting but declining the offer is not to be taken that way. Why?

One good reason is that it is interpreted to be an issue of deepest identity, in the way the offer of a drink cannot be, with one exception: if you offer a recovering alcoholic a drink knowing the person is a recovering alcoholic.

The issue of deep identity mixes with the iron law of reciprocality in this way. If we both know of the rule of reciprocality, then you are offering me oral sex with the firm expectation that I will reciprocate. In other words, the person who offers appears to be sending the message: I am homosexual and so are you. If the second person is homosexual, no problem. But if he is not, then being 'called' homosexual (at least by implication) is an insult.