I know when I was a smoker, anything that reminded me of the ill health effects of my addiction scared me. That fear came out as anger, and I'd often lash out at the people speaking truth to me, regardless of how kind they were about it. Without any further context, I'd say their anger toward you likely isn't personal, but a result of the fear they feel. The most I think any person can do is to remember empathy and do their level best to speak the truth as they understand it in as kindly a way as possible, without sacrificing the truth for the sake of being nice.