The issue isn't with cyclists being on the road, it's with them blocking the road while going significantly slower than traffic. Motorbikes aren't a similar problem because they're quick enough not to disrupt everyone else on the road.
Edit: For the benefit of the downvoters - I'm a cyclist, you dopey fucks - I'm just honest about the issue drivers have with us. Making up this bullshit just makes us look like liars that don't understand the people we're sharing the road with, and our reality-based arguments work perfectly well. Be better.
What are we supposed to do? We can't cycle on the sidewalk, and if we get closer to the curb, it gives many drivers the false impression that they can overtake without crossing into the other lane, not to mention all the potholes, drains, and trash that we then have to cycle over.
It seems like a dick move, but I promise you that most cyclists are purposefully being in your way to make sure you notice, slow down, and give us space. We're just as unhappy about being around your car as you are to see us. We'd happily fuck the fuck off to our own little lane if someone gave us one.
I'm a cyclist too - it's not an easy situation. It's easy to say the answer is good bike lanes, but we've also got to deliver on that. I'm the meantime, it's a case of riding responsibly on the road - without inventing unnecessary, dishonest strawman arguments about what concerns motorists. That does more harm than good.
Oh - absolutely - I just think that grounding the argument on this dishonest nonsense only undermines a good idea that can stand on the reality of its merits.
...those downvoting a simple reality-check from someone that otherwise agrees with you only demonstrate a willful disconnect from reality.