I don't think it much matters if the issue is that the son is gay, or trans, or changing religions, or changing politics, or whatnot---- if whatever it is, whoever the son has realized as an adult he is, is something/someone that the mother (parents?) were very opposed to or disdainful of throughout his childhood, well, that in itself is likely going to make it very hard for the grown son to feel close to his parents---and really, it should not come as a huge shock to parents if that happens. If you raise your children telling them that XYZ things in the culture are sinful, or wrong, or hateful--you take a risk that they may grow up, realize they are XYZ (or decide they are, depending if we are talking politics instead of orientation for example) and then the obvious message they have heard throughout their life is basically that you reject THEM.
That is not always easily undone or changed. Some people can move past a lifetime of comments quickly, but others need a lot of time to do so, and if the parent hasn't really changed their attitude, well, I would think more often than not that would make it even harder for the adult child to still feel close.
And I do get the impression that SOMEthing about the adult child's life really bothers the OP. And to make matters worse, she can't even accept that her son is making his own decisions and expressing his own self--she blames "outside influences" (which, yes, could well be the person her son is dating), which just shows a continued lack of truly understanding and accepting and loving the son for who HE is and what HE feels and believes.
And yet, the son must still love his parents--he is willing to make family enough of a priority that he will be there on Christmas for a few hours. He still responds to texts, etc. It does not sound like all hope is lost, nor anywhere close. But, I would hope OP could really look at the messages she is sending and has sent and take stock of the hurt that might have unintentionally been done and realize wounds need time to heel and she needs to be grateful for the time she does get, not push, and work on changing her reactions to her son and his significant other to ones that really feel comfortable to them. It'S probably not going to happen overnight, but it can get there if she tries. (so take heart OP

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