@Froggyrules Inui-sensei is out here talking about this guy years after the fact, she drew a comic about it to exemplify bad behaviour and literally said there are plenty of people who would be hurt by his reaction, to the point she even worried her gf was affected... How much more clear can it be that he drew a ton of attention and that it was extremely rude? Even his own gf is shown to be angry/embarassed by him and he seems to not be able to take a clue.
This kind of stuff is othering, it makes you feel like you don't belong, like you're not 'normal'... Don't do this.
Nobody is asking you to completely vanish the thought of surprise from your mind, cause you can't control that, but you very much do control everything beyond mere thoughts and this dude was an ass who caused a real scene. Even if it's the first gay couple he's seen IRL in his entire life, so what? He's not five years old, he should be past the need to point out every single thing he sees for the first time and especially so when it's not a thing, but a person.