They have been engineered to accommodate cars, so now they're undergoing a renovation for bikes.
Good! Renovate them to accommodate bikes. That's great, do more of that. But "sharing the road" is a terrible solution, which leads to the honks and dangerous situations the OP described. Neither the biker nor the drivers in the OP's post are in the wrong. It's just a really terrible situation that really should not happen.
In the OP's situation, the drivers that exhibit aggressive and dangerous behavior are clearly in the wrong. You could argue that their frustration is understandable, but their behavior is certainly wrong.
Share the road works fine as a solution without dramatically overhauling current infrastructure. Just don't be a mean driver.
It works fine if people adjust their expectations. Cyclists in the way rarely cause real stretches of backed up traffic. Your average speed might go down slightly, big whoop.
[Lots of places beg to differ](https://www.treehugger.com/bikes/dutch-kids-have-different-r...).
You can't bully people into being good, but there are lots of nudges like education and more thoughtful design that can move culture to work better.
If they do share that traffic lane, bad things will happen. Humans will make bad decisions, because humans are dumb and fallible. My point is that situation should not occur in the first place. It's engineered to fail, and sure enough, it does.
Source: Bikes daily in Boston, Cambridge and Somerville on a bike share bike. Passes cars the entire way.
In a perfect for me world the CBD would have zero cars and everyone would be on bikes, foot or mobility devices after they parked on the CBD fringe carparks or caught public transport in.
That will never happen.
So the next best step for me is dedicated bike lanes separated with enough room for everyone.
More likely, but not everywhere is getting this right or has enough space.
So what we have to work with until something better arives is what we have now. Cyclists don't want this any more than you do but this is what we have and we would just appreciate some understanding. I try to get out of the way as soon as it is safe and I make sure I am at least trying to keep pace. I have never had cars behind me for more than 30 seconds and I honestly don't think that's much to ask for my safety and ability to get to work. If I were in a car you would be stuck behind me the whole way and then I would take your parking spot.
The thing, I want to commute to work today. Do I just stay home and yell at politicians until a lane is built? Or do I legally use the existing roadways?
And once there is the precedent that cyclists ride only in dedicated bike lanes, then you've limited the area that cyclists can ride to dense, affluent areas that have the demand and money for dedicated bike lanes.
Shared space doesn't mean "shared with other auto drivers only."
For roads where there is street parking you simply dedicate that for bike lanes and force car owners to use the more expensive parking houses. This influence the commercial flow a bit unless the space between parking houses is minimal in commercial districts.
In proportion to bike ownership you also need to remake roads which are too narrow and make them dedicated bike lanes. The proportionality clause here is really important to balance the interest of both groups if we want to view roads as incompatible to be used by both.
Of course if cyclists can rely on cars to pass them carefully, they can move all the way to the side to let the car pass. But that doesn't work with aggressive car drivers.