Alright... let me see if I understand you correctly:

Your argument is something along the lines of:
1) Jesus calls people to either heterosexual marriage or celibacy, according to a person's strength to remain celibate.
2) Homosexuals whom God does not change (at least to some degree) cannot enter faithfully into a heterosexual marriage.
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3) All such homosexuals are called to celibacy.
4) God will not burden us beyond our capacity.
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5) All such homosexuals are people who do (whether or not they are aware of it) have the strength for celibacy.
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6) Homosexual behavior (being outside the above defined parameters) is sinful.

Unless you wish to bring an argument against the ones I've brought (at various points) regarding the oft referenced Genesis and Leviticus passages, and the definition of arsenokoitai/es, then your argument is circular, because 1 presumes 6 (I have already shown that this passage can be interpreted as permissive of homosexual marriage if homosexual behavior is not essentially sinful.).

In addition, it seems unrealistic to assume that all homosexuals not helped to change to be able to marry heterosexually are wrong in their self-assessment of their strength. After all, we trust straight people to identify their ability to be celibate or not.

Moses found, when it came to it, that he did have the strength after all, because God had given it to him. Why, then, do (many) Christian homosexuals not find this strength when faced with the challenge?

In Christ,
~CSL

P.S. to refresh about the arguments I have brought (in large part) see www.inclusiveorthodoxy.org   www.inclusiveorthodoxy.org  , esp. under "The Bible & Homosexuality".