To each their own, and fortunately most(all?) editors allow such features to be turned off.

On the other hand, I find the "frivolous indulgence" perspective extremely obnoxious along with the related implication of moral or technical superiority of not using syntax highlighting.

As a side note, the way it helps many people who prefer it has some fascinating cog-psych underpinnings: https://en.wikipedia.org/wiki/Visual_search

Sometimes I wonder if those who don't prefer it might have some synesthesia which might allow their brain hardware to provide what the syntax highlighting does for the rest of us.