Did it scratch yours?
you're questioning the durability of the frame based on possibly superficially scratching it with a micro usb connector?
I think the durability of the aluminum frame will be an issue should you dent it to the point where it lifts or deforms the devices remaining body bits along with it.
Aluminum is aluminum. Not the strongest metal in the world and it does scratch and dent. I guess the best thing to do is be careful with it. Not to the point of babying it but if scratches stir your inner OCD, then use caution when inserting the USB. Aluminum is durable enough for this application. For what it's worth, aircraft body panels use aluminum.