Handwriting is inherently ableist. A portion of the population is blessed with the inherent ability of fast, legible handwriting. A portion of the population is not. Typing is an equalizer that allows more people to participate in the conversation.
If this were the only option, sure. It's not - the article points out several other possibilities. Just because one option isn't accessible to all doesn't mean we have to accuse the author of being ableist. We don't take away writing from some people because others can't do it - we provide alternatives.
I hope you're joking. In case you're serious, the same argument could be made about typing, speaking, or really any related activity. Or communication in general.