i think what they did is a bunch of bullsh@#.
im in texas but from what i know, i could not put anything in an employees review that had not been previously documented. it had to be a "write-up" and had to be signed by the employee, so it was not a shock or suprise when it was on their review.
sounds like u never heard them say anything about your "tone" before, which is why u are shocked and surprised by their comments . can u say...DISCRIMINATION????
it sickens me that one or a few people can make someone doubt their ability. but it happens everyday.

andy was demoted from area GM to an asst. SM, the DAY BEFORE his treatment started. they said he needed more training. although before his diagnosis, they gave him several positive reviews and thought his shit didnt stink! he never had ANYTHING negative said before this. after talking to HR (waste of time)he filed with the EEOC citing discrimination--they took his case. it is still pending.
DONT take this lying down...u do have rights...as eric stated, just research what they are.
good luck!