One thing that has changed my perspective a bit is the concept of "emotional intelligence". After evals at work, I found out that I rate relatively highly for emotional intelligence but didn't realise it, so I'd always assumed other people were much the same as me -- so people being irrational like this always irked the hell out of me because they just seemed to be assholes.

In my current job I've had a lot more exposure to the concepts of emotional intelligence and what it's like when people don't have it. I was kind of shocked at how un-self-aware and un-reflective most people are! (Edited after the fact to add: this was not meant to sound as judgy as it did; merely a reflection on the fact that my assumptions about other people were entirely incorrect.)

So now I sort of make a conscious effort to think "what might Grandma be feeling that she doesn't understand or hasn't identified, that is causing her to act in this terrible/ludicrous/ludicrously terrible way?" It's a surprisingly valauble tool when it comes to this kind of thing.

On the other hand, I entirely support anybody's right to draw a line in the sand and say "I don't care if you *mean* well, you're still *being* an asshole; go away and don't come back until you've grown up a bit". I'm just presuming here that the LW doesn't want to take the nuclear option if they don't have to. :)