Additionally, to me, red deletion doesn't mean "this was a bad action". It means "this was bad code, so we're crossing it out". Semantically, that makes total sense to me. Red is bad old code, green is new good code. Seeing a lot of red in code means the same to me as seeing a lot of red on a marked up copy of an essay (as long as it wasn't a professor who marked it up) -- I've identified a lot of improvements to make.
I do, however, believe the author has a very strong argument relating to code comments. I'd like to see a shift towards this style of highlighting in the future as I often find myself having to modify nearly every colour scheme I use to make comments far more prominent.
That said, it would also make sense for diff software in particular (as one of the most prominent software uses of red and green right next to each other for semantic purposes) to have an easily adjusted option for a different color scheme for the very common case of red/green colorblindness.