My hypothesis is that this is because they co-opted a lot of the civil rights movement to elevate some vague sense of "nonviolent protest" to the pinnacle of political action. Obviously this applies to more things, but calling your representative is just the peak of lib action.
Everything I say is going to be entirely vibes-based, but I feel like what the education system here taught about civil rights was a lot of "Rosa Parks refused to give up her seat and MLK led nonviolent protests and did that one speech and the nonviolent protests were so effective in the marketplace of ideas that we ended racism (oh and btw MLK was a moderate who would agree with Republicans today
)." Now libs basically think any action where you make a lot of noise without any material consequences is the best way to create change because everyone's a rational actor who will always choose the good ideas as long as you put the idea out there and "look!! it worked in the 60s!!" Couple this with the belief that we actually live in a democracy where the government will "listen to the people" and you'll get people calling their representatives and sending strongly worded letters


