Simple addon, and it works. Thank you so much for it, jscher2000!
Now sites won't know that I have ETP enabled, at least not by the presence of the DNT header.

Simple and very useful. Fx's Strict TP is very useful, but it enforcing the use of the DNT header just serves to set you apart from the rest, which is not a good thing. If most sites obeyed the header, Tracking Protection wouldn't exist in the first place. Thanks.