I touched on immigration in another response (see above) so let’s tackle affirmative action. First, allow me to approach it the same way I did immigration.
The 30,000 feet view is this: Republicans believe in meritocracy, where those who work the hardest and do the best should be rewarded for their efforts; that all people should be treated equally. An intelligent, reasonable person can agree with this. Democrats believe certain populations have been mistreated in the past and to compensate, accommodations or a helping hand should be provided in order to level the playing field. An intelligent, reasonable person can agree with this as well. Thus, an example where perfectly rational intelligent people can have differing viewpoints.
A specific example of Democrats in action:
While seeking the Democratic nomination in 2020, Joe Biden vowed to pick a woman as Vice President and to appoint a Black woman to the Supreme Court. Republicans I know despised the idea that in choosing the person one breath away from the Presidency, Biden would start by eliminating half (or in the case of the Supreme Court, over 90%) of the talent pool before starting his search, and that his first criteria would be gender or race.