Well they may have been lying? Not very professional, right?

We all have to vent. This is just part of the job for the therapist. On your next visit or maybe even prior to the visit if you feel you were in the wrong and being harsh you should write an email to follow up just letting them know your sorry, you aware of your actions and that maybe "?" triggered the remark or outburst.

Give it a try and like with anyone in this world you will find that forgiveness and apologies go much further than insinuations and negative remarks.