I understand your frustration. Mufflers get damaged during shipping all of the time. The damage that you have is completely reversible and will not affect the performance or aesthetics of the muffler. The bent tab is just a ground strap that probably stay "as is" or it could be bent back to the shape. The pipe itself can be easily bent back to shape with some pliers or a vise grip. You can go through the hassle of getting another one but there is the risk that that will receive damage as well even if its reinforced. Just my .02c.
Current - '11 e92 M3 SG/FR ZCP|ZCV|ZP2|2MK|494|415|6NR|752