Yes you can bend an ali prop and damage a composite prop by pulling on it. Prop shops do it all the time. It's called cold working. Looks like there's a lot of opinion here so without getting all technical I'll add this.
I've seen damage to both kinds of prop. Ali and composite.
Props are under incredible load during different phases of engine operation. Granted. But they are specifically designed to carry those loads.
If you point load a prop blade in exactly the right spot with enough resistance + force, you will bend it.
But most things people have said ring true and if you stick to your common sense, you'll never have a problem. ie; Don't pull a 421 out of the mud by a single blade tip and take extra caution with wooden or composite blades. Which are easily damaged by mishandling. I've pulled 3 composite props this year that have been damaged without the engine running.