I have run many bikes with battery chargers attached, with no damage to any components. The practice is NOT garranteed to ruin rectifiers.
However, if your battery charger put a high enough voltage on the rectifier, that would do it (exceeding the peak voltage rating). I couldn't predict damage unless I knew the specifications on the charger used or if the battery became disconnected from the bikes charging system.
Reversing the polarity, almost always destroys rectifiers and maybe some of the wiring, too.
You may have a bad rectifier. But, I think it best to charge the battery, and then check the chraging system with a multimeter.
Cheers,