The only way you're going to immediately hurt a modern engine running modern oils is pushing it super hard when it is stone cold, but all you folks idling the engine to two-bars are doing your bike no favors.
Other than internet urban legend, this is an area where the authoritative sources are in completely agreement: Start your engine and as soon as the engine runs reasonaly smoothy and will take throttle and light load (tyipcally almost immediately after starting) ride off. Ride very gently initially, but add load as the engine warms.
The rationale is quite straightforward: Idling is bad as the engine is designed to run at higher RPM with load. Idling at cold temperatures is worse because you're running a very rich mixture and combustion is poor - all this puts lots of nasty combusion byproducts on your cylinder walls and into your oil, diluting viscosity and spreading corrosive elements throughout your engine. Further, an engine that is not up to operating temperature hasn't established proper working clearances which means warm up is a period of extra wear.
So to minimize the time the engine is running cold, YOU WANT TO GET IT UP TO TEMPERATURE QUICKLY, and this means riding, not idling. Just take it easy for the first mile or so and don't hammer it hard until it is fully warm. Simple as that.
Not to mention that you'll save gas, reduce emissions, and annoy your neighbors a lot less, especially if you have loud pipes on the bike. When I motel tour, one night out of three, there is some numbskull (typically on a Harley with open pipes), who cranks up his motor at 7AM and then goes in for his last cup of coffee. Fifteen minutes later, his engine now badly overheated, he'll blip the throttle for a minute before finally riding off. By this time, everyone in the motel is both awake (whether they want to be or not), and has a terrible opinion of motorcyclists.
- Mark