Hitch carriers are safe when used properly, with the motorcycle correctly secured. If at any point it looks unsafe, or your motorcycle looks to be in danger of falling, then you might be loading a motorcycle that’s too heavy for the bracket, have loaded it incorrectly, or are driving in a way that’s not in line with the manufacturer’s instructions.
Motorcycle hitch carriers are 100% legal, providing that they don’t obscure a license plate or your rear lights—naturally, this depends on what state you live in.