This is a lifelong 'tastes great / less filling' debate topic.
My vote: +1 on B+W UV filters, unless a CPL is needed (in which case I swap them). Strongly recommend a CPL for macro, but less for color or exposure, and more for managing reflections in droplets of water, glare from leaves, etc. You should have a CPL for that lens in general non-macro use as well. (It's a fully functional 100 prime, right?)
My UV Rationale:
1) It's cheap lens insurance at zero IQ cost. Filters protect the front element from damage. Unless you are buying very cheap lenses, even pricey filters are cheaper to replace than lenses are to repair.
2) When air or a microfiber are not enough, I am far more comfortable cleaning filters with that ROR liquid than using that stuff on lens elements.
3) I don't like having to remember if the L lens I'm using has weather sealing that is filter-dependent or not, so they just all get filters. Easy.
4) Hoods sit in my bag. I have a 100% VF and have (I suppose) decent discipline with sun placement in the frame, and three of my lenses' hoods are nightmare to use with CPLs. However, if I was using a hood, perhaps I'd shoot with naked lenses.
About the only time I have naked lens elements is when I use my Lee 4x6 ND grads (i.e. way less than 1% of the time). That system requires adaptor rings -- a screw-in like a filter (but no glass on it) with a metal outrigger to receive the big frame to hold the rectangular ND grads. As I don't like stacking filters (annoying for threading/unthreading reasons), if I go ND grad it's a sort-of-naked lens in that dust/water can touch the lens, but the 4x6 serves as a physical barrier for drops, impact, finger contact, etc.