The prop driving the engine issue only applies to radials.
In line engines (geared or not) don't have any problem with this. Every time you downshift in a car, you are doing the exact same thing. Auto and airplane engines obey the same laws of physics.
For a much more in depth explaination follow the link.
http://www.avweb.com/news/pelican/186778-1.html
There are tons of myths about how delicate many engines are. IMHO, the main reason is that they sit unflown for much too long, and when they do fly, they are run too hot.