My father hates split infinitives. He can get passionate in his discussions about them. I've smiled and nodded, but have not been sure what they are. So, here are the results of my research:
Here's a link to the definition. So, apparently, an infinitive is something that is one word in many languages (but two in English --> to + verb). In the definition, they mention Latin and Greek, but my memory of French and Spanish (and, I would guess, all romance languages) recalls that all of those infinitives are one word.
So, I guess that the person who objects to them being split in English has just been so well trained in languages that have them as one word that it is almost a molestation (or, substitute a less delicate word) of the infinitive to have an adverb stuck in the middle of it.
eh. It is as it is.