Thanks, everyone, for your replies.
I have branded as a "Jammer". I was wondering whether I fit the profile of one. So far, I am safe.
I tend to agree with Dan. Aiki is about seeking the path of least resistance (changing directions) rather than going against the resistance. I get irritated by nage who jerks or bounces me around instead of doing a free flowing technique on me. To avoid injury, the jerking and bouncing cause me to stiffen up and assume a defensive stance. Perhaps this is jamming as far as they are concerned.
In that case, if you are a Jammer, then they are Jerks!
Some folk need to learn a bit of muscle maturity - to me the ones who drag and jerk you around are like toddlers flailing their arms about with full force and zero control
Fortunately most people get this control, but there are always a few who don't, in which case you have to do what you need to do to protect yourself