A variety of answers I must say.

. I'm only asking because I wanted some perspective. My father passed recently (he was 75). My mother, his current wife of 35 years, is 20 years his junior and have 2 kids together. His ex wife (also 75) came to my dads funeral. They were married about 14 years and had 2 kids. The exe is such a nice woman. She was very polite and loving. She tries to reach out to my mother but my mom can't stand her and basically ignored any kind words from her. I know it upset my mom throughout the whole funeral. Later she told me it was the rudest thing she's ever seen (her attending the funeral).
I feel more like what a PP said. These people at one point cared about each other. Had children together. And if nothing else just to be there to support her own children after the passing of their father. I felt it was in fact the opposite of rude. I don't know. Maybe I'm just a peace loving hippie. Why can't we just hug it out kind of girl.
Seeing my mom show her talons to a 75 year old lady (ex or not) is just immature and completely ridiculous. I could be wrong though. Please don't flame me lol.