If USDC is truly backed 100% as stated then it shouldn't be a problem. In fact it might help them gain market share if coins with less backing de-pegged. Though I guess it could also lead to a general loss of faith in stable coins and folks as a whole would shy away from them.

Either way, most stable coins are built on some form of trust, and I'm much more inclined to trust Coinbase than most others. (Disclaimer: I have no dog in this hunt, I don't own any crypto whatsoever.)