This would be absolutely perfect if we were dealing with reasonable, halfway-sane people. Unfortunately, and trust me on this, Taaj really isn't.That's how I do it though. I look at my parent's as individual beings and not authority figures. Not that I ever had much respect for authority figures in the first place, but still. I hear what they say and see why they say it. From there I discern their intentions given my experiences with them, their tone, and a few other factors. If they come to me with honest concern I am more than willing to discuss the issue or hear them out. I then let them know I will take that into consideration and thank them for their input. I have at that point allowed them to convey the point they wished to and that earns me a mutual respect that I am willing to not only consider my own perspective. I feel better knowing I showed respect and carried myself as an adult. If others are unable to do that it is on them, but more importantly I did not alienate people I care about which may make them push harder.
I also never raise tone at people or show an emotion in my face when discussing things with people. People find it difficult to manipulate others when they are able to discern what others are thinking or feeling. Depending on the person how how quickly they lose patience this is the only thing I need to do. When they do lose their cool I ask them to take a moment and collect themselves. This puts them off their guard, after all if they are yelling and I am not flinching then clearly they are not getting the result they are trying to achieve of bringing me down to their level. Respect in my opinion is often one of the best tactics to counter manipulation.
If they bring the issue up again I remind them of the former discussion and ask why they felt the need to bring up a previous discussion. That usually fizzles out the issue by drawing a line in the sand, although respectfully.