Are we defining the same thing? The word can be as clear-cut as it’s definition allows, people will fit that definition to varying degrees – some to the point where they feel the word is an honest description of themselves, others… not so much. In those cases we either need more words to cover the different possibilities, or we might be able to get along fine with the words we have and some qualifiers or explanation.

When it comes down to it, the meaning of the word “heterosexual” is clear. What’s not clear is whether every person describing themself as heterosexual entirely fits the definition. There’s where the spectrum comes in… you might describe yourself as primarily hetero but “curious”, or bi with homosexual leanings. The fuzzy edges aren’t in the words and definitions, it’s in the people. That may well mean we’re never going to give a perfectly accurate description of a person’s orientation with the words we’ve got, but we’ll come closer that way than by abandoning the idea that words have meaning.

Yes, there are social constructions around sexual orientations, these constructs might be widespread or filter into law, but they aren’t a necessary part of the word’s meaning, they’re extra meaning that we attach to the word as a culture. It can lead to dire places… especially if certain religions get involved in lawmaking… but still, not fundamentally a part of the meaning of “heterosexual” or “homosexual”.

hows [sic] your lack of education on the subject

No need for casting of aspersions. If you’re going to fall back on what is essentially “Well if you’d read what I’d read then you’d know how wrong you are.” then we’re done here because I’m not going to argue with someone who won’t deign to actually explain their position.

Edit: Damnit, hold still… if you’re going to post more while I’m typing then I’m going to miss things that want responding to.