It's not true. The user didn't accuse them of being culturally insensitive. Rather, he argued that that automating the conversion was fool's errand, partly due to the differences between the various RTL languages. He suggested that the Bootstrap team point users to quality RTL themes instead of releasing a shoddy built-in RTL implementation.
Perhaps this should be added to the list of instances of people dismissing valid arguments by labeling them polical correctness.
The authors are professors of philosophy. I find it unlikely that they have "missed the point of philosophy entirely."