It's a consistent problem with his approach, and at his age I'll say it's baked in. I don't want to relitigate ancient Irish controversies, or whatever the hell Gamergate was all about, but he takes up a cause, follows it obsessively, jumps in with the subtlety of a bull in a china shop, and divides all players into good guys who are on Team Glinner and bad guys who are to be smashed.
To be fair he's capable of reflecting on his behaviour, and making amends when he thinks he's wronged someone, but this might not be sufficient if he's been calling you a nazi for the past ten years.
I don't know what JKR is thinking, but in her place there are a few things I'd consider. One is that if you offer him support privately he will make it public, and mention it frequently. Another is that if you're on Team Glinner, you will get dragged into all his personal beefs whether you like it or not. And he doesn't seem to realise that, by constantly asking why she isn't publicly supporting him, he's putting her in a very difficult position.
TLDR: Graham doesn't really do subtle, and he's apt to see himself as the Main Character with little consideration for his impact on others.