Struggling with friendship drama before I leave for studies.

I apologize for my English; it isn’t my first language.
Hope he doesn't find out this post :(((

Background: I(f) was part of a friend group of about 12 people. I'm changing universities and leaving the country, while my close friend is staying in the same city. We recently became really close in just a month since could match our freaks. He really hated this one girl and said she's "attention seeking" and "always wanted the spot-light". side note: We're both gay and there's no spark between us.

Story: As I'm leaving, my friend wanted to go to the airport to say goodbye. I agreed and told him I would update him on who else is coming, as I have other friends from high school. When I informed the group about my departure, some of the girls expressed their desire to come to the airport as well.

I told my friend that the girls wanted to farewell me in the airport, and he asked if a particular girl he dislikes would be coming. I said yes, since she was one of the first friends I made at university. His reaction was strong: “If she’s coming, then I’m not coming.”

From my perspective, I felt she deserved to come, especially since she was the first ever friend I have made. To respect my friend, I considered asking the girls not to come. He then expressed his frustration, saying he was mad because she made it "public" and "crossed the line"

This irritated me because I felt I couldn't just reject her on the spot when it seems like she was acting out of kindness. I also didn't realise how much he hated her. He said she's just saying that to grab attention, and just wanted to be along for the ride. I told him he was putting me on the spot since I'm friends with both sides and that he was kind of overreacting.

He then said things that made it seem like he wanted to end our friendship, stating, "Okay, never mind, I’m not coming. We had our fun," and "It’s fine, we’re ending this." This felt out of the blue. I’ve had arguments with my other friends before, but we’ve never talked about ending things like that. It made me wonder if he might be dealing with some mental or social issues. He had previously mentioned that he struggled to connect with others in high school and felt like an outcast (he did say people were lowkey bullying him), even deleting every high school classmates that once followed him on Instagram. He also told me I was the first person to make him feel a connection.

Eventually, he admitted he was overreacting and explained that he hated her because he felt excluded from the friend group from the start. He revealed that they had badmouthed him behind his back, which explained his anger. I had no idea about any of this since I don't attend the same classes as them last semester and didn’t hang out with them much. I apologized, saying I didn’t know the backstory. He then told me he needed some time alone and said he understands that I understand the situation now. We haven't been talking for a day now.

tldr: I'm leaving the country for a new university, and my close friend wanted to say goodbye at the airport. He became upset when he found out a girl he dislikes (who's a friend of mine) would also come. After a heated discussion, he revealed that he feels excluded from our friend group and has been hurt by their actions. He admitted he was overreacting but asked for some time alone afterward.

This situation is stressing me out; my head keeps hurting and ringing since he has been a supportive friend, and I don't want to lose him. On the other hand, he is also acting kind of toxic. I’m just asking for advice on how to handle this moving forward. Am I in the wrong for being honest with him with my emotions, or should I actually just not say a word to defend the other girl?