The point is that we are seeing too much PC, and it is corrupting the nature of public debate. All comments become subjective to the audience, rather than subjective to the speaker. The examples cited by the author all are encompassed in the quote
" I think it’s these very small things that reinforce cultural and racial stereotypes.. "
to which the author disagrees. You are correct, there is no appropriate scale to measure being offended, which is why unchecked (read: no scale to judge) PC results in kids being kicked out of school, a huge industry being built around PC counseling, etc. The author is not proposing removing PC altogether, just that it is being laughably abused to the detriment of everyone.
I'd be inclined to agree.