It is nothing like that argument and I think you know that.

I think there is a difference here. Signal qua signal isn't dangerous. Its purely what one does with it that might constitute a criminal act. In particular, using signal is unlikely to cause problems accidentally.

Driving a giant truck for no good reason entails a certain risk because of both the inevitability of human error (on the part of the driver but also others) and basic physics.

Furthermore, one might argue that the right to private communication is more important than the marginal improvement in life that you get from driving a big car for no particular reason.

Like consider a person who wants to drive a car filled with TNT. By its very nature this is a danger to others regardless of the intent of the driver or other drivers. Society might be argued to have an interest in regulating such behavior. I think there is a good case to be made that unnecessarily large vehicles differ in degree only from the TNT case, but differ categorically from using signal.

I'm not making the case that the differences justify banning big cars, but there are differences between the two situations.

Complete indifference to a big increase in deaths?