Had the same question with "Are you gay when you like anal sex as a men?" ^^ I mean, why should a men fuck a woman in the ass? Hew could do that also with male x male without wasting the unused pussy at that time.
Short answer:
Gay.
Long Answer:
Lets start with a few facts.
1. all Futa are male genetically. They all have a "Y" chromosome.
2. Yes, some are raised as females. That doesn't change fact 1.
Then there is the aspect of if a male mind can exist in a female body and vice versa. I'll avoid that aspect because many people will simply argue and ignore facts related to it.
Bisexual in my book means gay. Most the bisexuals I known in my life went back strait. (call it faze or experimental period). Those that didn't most went full gay. Maybe 1% to 3% stayed Bi. But do gays have strait sex? Yep, I knew plenty of gay people that had strait sex not because it was enjoyable to them they did it for one reason or another most commonly money. So calling oneself Bi vs calling oneself gay doesn't hold any real difference in what I seen.
(That is my personal experience yours is most likely to differ. I don't mean this to insult anyone. Just a personal observation.)
Then you have the aspect of mental state of the viewer is also going to play a role.
Take if the viewer is using the male as a place holder for themselves and what their actions may be. That would be different from simply enjoying the male have sex with a female.
Personally I don't like images of a woman with more than 1 male in it all. How can I be two people. I guess I could clone myself and come up with some mental story like that but to much work. So I tend to think guys that share a woman or watch videos of a woman getting gang banged are as gay as those who like Futa. Consider the simple aspect of how much of the image is filled with male body parts vs female. Are they really there to watch the woman when 2 or more guys are in the scene covering most of her up.
We can follow that up with a guy who likes watching his woman with another man as being gay.
A guy who wants to share a woman. Gay.
The Futa body is not like a female body. Like someone claimed above. No female has a dick. A dick and a strap-on are two very different things.
Also if a female is using a strap-on to fuck some guy up the ass that is gay. Watching it is also gay for a male.
Two futa going at it is also gay and so is watching it.
So a guy and a futa going at it regardless the direction is gay and so is watching it.
We can expand that further a male with a trans is gay no matter the direction of transition.
In one case you are fucking a male with a "Y" chromosome. In the other aspect you are fucking someone that looks like a male.
Either way gay.