And I have never in my life heard anyone say "DE-fend" Hoo boy, you must not have heard many Southerners ('scuse me, Pook and Olly--shoulda said U.S. Southerners!) talk, then.

The real question is not "have I split an infinitive" but "have I communicated the real meaning (and or emphasis) of what I want to say."
Mm. As someone (sorry I've forgotten who) pointed out not too long ago, it also depends on the circumstances: are you talking or writing, and is it formal or informal?