The issue with buttons/adornments/attire has to do with humility. Anything considered prideful (including buttons) is to be avoided. They dress so as to avoid drawing individual attention to self within their community.
While you may consider their lifestyle not in accordance with Sacred Scripture, they would likely disagree, and cite Rom 12:2 and 2 Cor 6:14, 17 and other passages. That's if they decided to respond at all instead of accepting the misunderstanding in silence.
Their selflessness in helping their own and outsiders is unparalleled if you ask me. Even though you've spoken unkindly of them, they'd be the first to help you if you were stranded by the road or otherwise in need of assistance in their power to give you. Unlike many of us English, they don't evaluate someone's worthiness of assistance before rendering it. If that's not living the Christian message by example, I don't know what is!
Peace be with you.
Criticism is not unkind. When is the lat time you heard of an Amish missionary?