That's not true. The Dixie Chicks wasn't all that long ago. They also have protested plenty of movies and other media over the decades that offended them.
As you say the Dixie Chicks "wasn't all that long ago" especially compared to the Left infiltration of, for instance Hollywood, going back to the 30's if not earlier of the 20th century. One also has to take into the account frequency of outrage and intensity which is part of the reason I specifically said "broadly speaking" in the portion you quoted. I'm sure you can find examples of someone, somewhere objecting to some current outrage even, at some points, to some success. But these were typically isolated, specific incidents lacking the uniformity and purpose of the Left.
Its not the Right who'll trawl a comedian's twitter to find some joke they made five or ten years ago and then cancel them over "wrongthink". Its rare up until the current era for the Right to boycott an entire company merely because of political pandering in their ads.
Simply put for the longest time to offend the Right carried little risk and what little it did was typically quite short term. So if you did get blowback you just run a couple of ads with cowboys or American flags and that would usually settle matters. While to offend the Left would be to have your reputation run through the mud on twitter and the media and your products boycotted until you groveled and debased yourself sufficiently for your "mistake". So its little wonder most companies tilt Left even before accounting that they have been marinated in that ideology since likely their birth.