My (24 M) friend (28 M) did something so fucked up to a girl and now I don’t know how to interact with him anymore, can I get advice on how to deal with this?

This story was previously on AITA but it got removed.

So this is not something I did but a friend consulted me about what he did and I can't even talk to him properly after it.

My friend (28 M) was talking to this girl for a while and the girl was engaged which is already fucked up, the girl and him clicked and started hitting off for a while. Then the girl leaves her fiance because of reasons he did not clarify.

So now it gets serious, they keep on talking for 3 months. Then, the girl tells him that after she had some issues with her health she did a check up and found out she had stage 3 breast cancer.

He said that he was devistated to hear this but kept talking to her, minding you till now they were not official. After a period they decide to get into a relationship and they seems pretty happy.

He then says that "I thought about it logically" and then after that he decided to leave her, and not even leave her … Fucking ghost her!

I was so fucking pissed at him but I didn't say shit, but now he's asking why I'm not talking to him and that he feels terrible for doing so.

I fucking hate when people justify their bullshit with the "I'm logical" claim.

Wtf should I say to him?