Or, to phrase it another way, does the fact that some QSRs serve healthier food make it more acceptable/less bad to eat at those places?
The answer would seem to be almost necessarily Yes...BUT, cutting even 10% of the empty calories in the food is not going to result in good and healthy food, just food that is (marginally) not so bad and unhealthy. A Snickers bar is probably more healthy than a marshmallow because it contains nuts which contain minerals, etc., but that doesn't mean it's advisable to increase your daily intake of those candy bars.
"Don't you ever underestimate the power of a female." Bootsy Collins