I think it depends on context and tone. A sarcastic, "Dear," would live me spitting blood whilst a friendly tone with the same word wouldn't bother me at all.
I can't remember the words used at our son's college Parent's Evening but I do remember both my husband and I being astonished at the address by the lecturer to us as we walked in and out. We both felt it was completely unprofessional and when he couldn't give us examples of our son's "disruption" of the tone of the class, we were completely perplexed. He wasn't being loud (something I could visualise), he wasn't getting up and moving about the classroom when he shouldn't be, he was always able to complete the work and he hadn't made any disparaging comments about the lecturer that he could hear. Finally, when the lecturer actually swore in his summary and called me "Love" and offered the only hand shake to my husband, we just decided he was a Tosser!