i don't think it's a matter of guilt versus education at all. i don't want any FF mom to feel guilty. guilt accomplishes nothing. i want moms to truly know the facts about breast milk and formula, and also to have all the support they could need to successfully nurse, and then make an informed decision.
i think if moms knew the truth about each, and knew how to BF (weren't told undermining things about 10 minutes per side or not letting the baby use you for a pacifier, etc., etc.), a lot more women would nurse their babies for a lot longer.
as for those who would choose formula anyway, there is no need for guilt. i assume if you do what you think is right for your situation, you would not experience guilt. i don't feel guilty for having a c-section, for example. i feel disappointed and regretful, but not guilty because i did the best i could.
but i would never say c-section is as normal and as healthy a way to birth. it's not. it's necessary in some cases, and lifesaving because of that, but in most cases it's not necessary and it can be harmful. just like formula feeding. and even though i had and needed a section, it doesn't mean i can't say they are an inferior, less normal way to birth.
for me it comes down to not taking the facts personally. if you need to use formula, that is fine, and thank goodness it exists!--but it doesn't change the fact that it is typically not necessary and is biologically inferior to breastmilk.
ETA: and i agree with PP that a lot of the problem is social context. i think workplaces need to ALL be friendly for pumping and storing milk, for example. breastfeeding is a health issue AND a basic human right for babies and mamas. there is no excuse for these cultural barriers that make it so hard for mamas to choose to do the most natural thing in the world.