I shouldn't have to, so I don't, and they eventually do leave.
>Gotta be brave and interact with the world sometimes. reply
Telling a salesperson "fuck off" doesn't take more bravery than I have, it takes more effort than I am willing to expend on advertising.
I have a no soliciting sign and those who ignore it (basically all of them according to camera events) are 100% in the wrong, are being rude, and do not deserve a wave-off.
However, in general, the decision to answer or not answer a salesperson at your door is not about bravery. It is primarily about effort and annoyance.
The combination of "Is it really that hard to say "Selling something? Not interested, have a nice day!"?" and a condescending "Gotta be brave and interact with the world sometimes." rubbed me the wrong way.
It did me, as well. It smelled of someone projecting their insecurity onto the general public.