old vs young (as with so many other social cleavages) is real, to an extent, but nothing compared to the wealth oligarchy vs. the rest of us. These cleavages are pushed intentionally to divide and conquer.
poor (and even moderately wealthy) old people aren't the enemy.
True, but there's an inextricable link between life expectancy and wealth that can't be ignored and a very strong positive correlation documented between the two. Poor old people aren't the enemy as they never had power to begin with. Wealthy old people, on the other hand, represent one of the most regressive voting blocs in American politics, and have voted largely to expand the power of the wealthy.
They also love to determine their vote based on social issues rather than economic/political issues. I blame religion but regardless of the cultural motives it boils down to echoes of racism/xenophobia from their parents' generation.