If you send something illegal to a public mailing address, does anyone associate that material with the owner of the address? No. It's the sender associated with it, not the recipient.

Also the utxo is spendable, it just doesn't make economic sense to spend it. Remember that a transaction can have multiple utxo's as inputs so you could add a 1-sat utxo as one of multiple inputs and that would spend it.... not that it would matter.