I've been a professional photographer for 29-years and have used many, many Hasselblad, Nikon and Canon lenses for decades. Many of those lenses cost more than a Mavic2, and many cost more than and
Inspire 2, and I've always been a purist. I use no filters on my lenses, never have, and have never damaged one. I've probably owned 40 lenses. I've never had bug smacks or any other issue besides just a need to do a good dusting before shooting. You can certainly damage a lens if you hit something harder than the glass. But it's kind of difficult to hit your Mavic lens on anything besides maybe a tree branch or some grass. I mean, it's kind of protected up in there.
I'd suggest that the filter on the M2 really isn't going to impact the image quality in a quantifiable way. As excited as we are about the M2 Pro with its larger sensor, the image is still not as sharp or good as a top of the line Nikon or Canon. In one of those cameras, you might be able to discern the difference between UV filter and no UV filter because the image is so much better. But in these drone cameras, even being that it's a Hasselblad lens, any degradation from the filter really is going to be obscured by the less than perfect image quality anyway I believe.
We, professional photographers, do argue from time to time as to whether a UV filter (albeit...another piece of glass between the sensor and the subject) helps or hurts anything. When it comes down to it, usually the difference is so minute that you almost need scientific equipment to detect the difference. Regardless, I have just never used any kind of protective filters.
The only problem I see with flying the M2 without the front filter is that it really wasn't designed to fly without it. It's possible some dust could work its way in and get to the sensor. That would not be a good thing as I'm sure it's impossible to clean the sensor yourself.