On any road with a speed limit greater than 35mph, bicycles ARE slow, period. Especially with the addition of an uphill grade, say 6% or greater. And I've even seen bicyclists dismount and walk the bikes if the incline is steep enough, say over 10%. But that narrow motorcyclist has the motor capabilities (e.g., not strictly powered by human power) to keep up with traffic. Furthermore, motorcyclists have to get a license to legally ride on the public roads with motor vehicle traffic.
In contrast, any person can learn to ride a bike, then ride on the road whenever they choose to--no license required.
And if you impeding traffic, you should be turning out (i.e., pulling off the road) to allow the thru traffic to continue. The lane is not yours in any case where you are not able to keep up with the flow of traffic.
But as far as the government is concerned, I think their choice to place a side lane along--but at least hypothetically divided from the regular flow of traffic--is a good idea, since bikes pedaling their chain-buttisted-frame-mounted-two-wheeled chair is more akin to running (i.e., pedestrian behavior) rather than actually diving in a motor vehicle sense.
It is when traffic is impeded, the bicyclist refuses to turn out, and traffic is de-facto forced into crossing over a lane marker to the left in order to continue at the speed the flow of traffic is intended to flow.
And it definitely is arrogant--and should be outright illegal--when packa of bikes spill out of the bike lane into the flow of traffic.