Refined flour is made out of the endosperm of the grain kernel, and according to this article, the lectins are contained in the germ of the kernel.
It just makes me wonder, what are good reasons for avoiding refined flour if these problematic parts are removed?
a) you've still got the gluten mixed with the starch;
b) refined flour will spike your bloodsugar quicker than almost anything else;
[edit, kudos to Happy_Now for this one] and c) since your refined flour is now devoid of any nutrients, it will replace otherwise nutrient-rich foods (unless you do not care about how many calories you eat each day to meet your nutrient requirements)
If you need more infos on these, archevore and fcourse paleo hacks are full with all the knowlegde and personal testimonies regarding gluten or blood-sugar induced unpleasantness.
I say its obvious... its a processed food that has very limited nutrition.
If you are 100% certain that your body does ok with a slice of white bread then consider eating it after an intense workout.