Toshinori Yagi/All Might:

He was shocked to hear this and also disappointed in his fans. So he posted a video of him saying about how he loves his lover very dearly and his fans shouldn't hate on you for loving him but instead support the happy relationship you two have before he ended it with a big grin and a thumbs up, assuring those "fans" that they do not have to be jealous because they will also find true love one day, which definitely isn't him because he's happily in a relationship with you.

Shota Aizwawa/Eraser Head:

He never shows his face on the media, but this was the one time he did. He just filmed a video to tell those people who are his "fans" that he doesn't want them so they can stop hating on his lover and leave. When you told him he shouldn't tell people to leave, he told you he doesn't care about fans and all that stuff so it doesn't matter.

Hizashi Yamda/Present Mic:

When he heard, he gave your forehead a kiss and told you not to worry about that. When he was on his talk show, he said he noticed some mean comments made towards his lover and he really does not appreciate that and that true fans wouldn't do this or even care about his love life before he excitedly said this won't stop the love between you two though and this will just make him post more adorable pictures of you two together to make those people more jealous before he played many love songs while uploading many cute/funny pictures of you both.

Nemuri Kayama/Midnight:

She will gasp when she found out, angrily saying these people are rude and you have to ignore them because they are just jealous. She will post a sexy picture of you both and put an annoyed rant under it about how she's happy with you and anyone who hates you for simply being happy with her can stop now because neither of you care and it's simply a waste of time that they could spend trying to become a better person.

Keigo Takami/Hawks:

He will tell you to ignore them, saying just some jealous people who can't stand that two gorgeous people are happily in love. When he sees you get upset or insecure while reading the hate comments, he will be quick to throw your device away, using his feathers to catch the device before it can crash on the floor, and begin covering your face with kisses, telling you to ignore those people and telling you that he loves you.