Why should anyone be offended?
Because he implied there's something bad about interpreting Sam and Bucky as being gay or bisexual or pansexual. Had he just said, "You know, I personally don't agree with that interpretation, but it's a valid way to interpret the characters if that's what works for you," it wouldn't have produced such an intense backlash.
He's the actor portraying the actual character, and he should be the one to know whether or not said character is homosexual or not.
That is not how art works; if a work of art does not outright
preclude something by directly contradicting it, then many different interpretations of a work of art are valid. There is nothing in the text of the MCU that precludes interpreting Sam and Bucky as attracted to each other; ergo, neither Mackie nor anyone else definitively "knows" if Sam and Bucky are gay/bisexual/pansexual.
If some fans are saying, "Hey I think The Falcon and the Winter Soldier are homosexuals..."
You realize how outdated it is to refer to people as "homosexuals" outside of highly technical contexts, right? It's borderline offensive to many gay people because it's a term that was historically used by people who hated them and wanted them to cease to exist. I'm not saying this to be mean-spirited or disagreeable -- I'm saying this in case you're unaware.
And the main actor of one of the character hears about this and responds with: "No. The character I play isn't homosexual..." (Unless he did so in a derogatory manner of some kind); there's nothing to be offended over.
Except:
1) Art is a form of communication, and it is the right of every audience member to interpret a work of art uniquely. Unless the work specifically takes an overt, textual stance, any interpretation not explicitly contradicted by the text is valid. Ergo, while it is
not a valid interpretation of
The Falcon and the Winter Soldier to say that it's racist against black people (it textually takes an overt anti-racist stance), it
is a valid interpretation to view Bucky and Sam as gay or bisexual or pansexual (nothing in the text establishes them as
not gay or bisexual or pansexual).
2) While he did not outright say there's anything wrong with being LGBTQIA+ by itself, Mackie's choice of words
did imply that there's something bad about interpreting Sam and Bucky specifically as being gay/bisexual/pansexual in his choice of language. That's pretty offensive to people who have been denied meaningful representation and who are doing this interpreting because it fulfills an emotional need not to feel invisible to society at large. He could have said he disagreed with that interpretation without saying that it was somehow bad or invalid.
3) The very fact that Marvel does not have any major LGBTQIA+ superheroes in their movies or TV shows is itself pretty damn offensive. LGBTQIA+ people exist, they make up a large percentage of the population, and they deserve representation.
Can’t we just have characters be gay, straight or otherwise without reactionary anger about both too much and too little representation?
Not in the context of the creators' culture being deeply cisheterosexist for thousands of years. There is no neutrality here: You either: 1) embrace equality for LGBTQIA+ people and thereby feature depictions of LGBTQIA+ characters that are equal to those of the straight characters, or, 2) embrace inequality for LGBTQIA+ people by depicting them in a marginalized fashion, by depicting them negatively, or by not depicting them as existing. If you go with the former route, you are going to make cisheterosexist people angry. If you go with the latter route, you are going to make LGBTQIA+ people angry. The only way you can avoid angering anyone over this issue is if cisheterosexism disappears in the culture in general.
If a writer wants to add gay characters, it’s their own creative decision, and if the writer decides their characters are straight, it’s exactly the same. Just enjoy the characters for what they are instead of trying to politicize every little detail of their identity.
That's easy to say, but a lot of LGBTQIA+ people interpret characters as being LGBTQIA+ because there is a deep emotional need for positive representation in popular media that they don't get, because media traditionally either ignore, marginalize, or stereotype LGBTQIA+ people. Those of us who are cisgender heterosexuals don't have that problem because we see ourselves represented in media all the time and have ever since we were children. The very act of
not depicting prominent canonically LGBTQIA+ people in major media like the MCU
is itself a political choice.