The benefits of getting more of the population to cycle are so beneficial that it's a joke to even try comparing the return on investment of cycle lanes versus car infrastructure and of course, when there's lots of cars, it pretty much pushes out other forms of transport due to the size/weight/danger/pollution of the cars.

Here's a somewhat biased look at the economics of cycling:

https://www.cyclinguk.org/briefing/case-cycling-economy

> "Bike lanes in my country are mostly paid for by taxes on cars and petrol"

Governments get money in, and they spend money. There's no real sense in which "bike lanes are paid for by petrol taxes", nobody can prove it either way by measuring anything - that's a matter of where they write the numbers in a spreadsheet - it's not the same money, as long as all of it balances. It's an arbitrary accounting choice and you're choosing to raise it as a talking point because it makes car drivers mad, not because it has real world consequences.

> "The costs/benefits are often justified by cherry-picked benefits (e.g. reduced car congestion, or reduced pollution)."

The fact that you default to "the current level of car pollution with tens of millions of cars everywhere is the default" is a bias. That you think "reducing pollution" is cherry picking is a car-bias. That people have to argue for being able to breathe without getting lung cancer as a "nice to have" against a default of cars-for-everything is a massive bias.

> "The congestion arguments anecdotally appear to be lies: low usage priority cycle lanes seem to cause extra congestion (through phasing of lights and islands and other traffic controlling features)."

Public transport (which I will include bike lanes, pavements, sidewalks, L-trains) need to go from where people are, to where people want to go. It's a very car-biased talking point that a city put a bike lane from nowhere to nowhere, and look! The cars are inconvenienced and hardly anybody is using the bikelane, so bike lanes must be the problem, get rid of it. You can't just slap a bike lane in London, decide nobody is using it, and get rid of it. You need enough bike lanes that people can get from where they are, to where they want to go, safely - feeling safe, well lit, clear of mud and snow and muggers and not along a main road - and enough of those safe journeys for long enough that people can change their behaviour. Several rounds of New Year's Resolutions to get fit, months of seeing family and coworkers gradually cycling, increasing numbers of cyclists (or walkers) normalising it, seeing "normal people like me" bringing a bike to work or to the shops not just lycra clad idealists - for large numbers of people to move from car to (foot/bike/bus/tram). Amsterdam started changing towards encouraging cycling in the 1970s and it didn't get a reputation as a bike city for decades. Cars have a hundred and twenty years of being entrenched, multiple generations of people who think cycling is for children and the roads are too dangerous to cycle (they are!) which needs pushing back against.

> "Try and fairly point out that the numbers are juggled and you'll get skewered by cyclist ideologues."

I don't know if you can justify "existing without breathing car exhaust" in economic terms. I don't think one should have to. I don't think one should justify bike lanes in terms of reducing traffic congestion - moving people around effectively needs city planning overviews, zoning changes, joined up public transport where the schedules line up, until it overall becomes convenient to move around without driving. Bike lanes and cycling can be part of it, but you can't justify one bike lane or project in terms of reducing congestion. If one demands that bike lanes be justified in the framework of "good for car drivers" and then rejects the numbers because they've been juggled to fit in terms of "good for car drivers" when that really isn't the point at all, that's not balanced or unbiased.

> "I'm not against bikes. I'm against badly biased reports : towards/against both cyclists or cars."

It's just convenient that dismissing badly biased reports towards bikes means nothing changes, and dismissing badly biased reports in favour of cars means nothing changes, and that continues car dominance, which is nice.

Even starting the sentence "I'm not against bikes" is a bias. Cars parked up and down both sides of every side-road. Solid slow moving car traffic for multiple hours in the morning and evening every weekday. Billions spent on multi-lane motorways moving massive cars with a single person in them. Young drivers revving the bollocks off their engines at midnight, motorbike riders with exhaust volume increasers, pollution, road accidents, burden of cost on car owners, and you start with "I'm not against bikes". It's the millionaire saying "I'm not against helping the homeless, I just don't like the way they're asking for help. I'm just being unbiased and fair".

> "Balanced discussion seems so difficult."

It isn't a balanced world, it's a car-dependent, car-dominated, world, deliberately, by car advertising, governments subsidising car manufacturing, car company lobbying, car company bribing, and capitalism framing everything in terms of profit and having nothing in terms of community, quality of life, wellbeing, welfare, health. It's not an accident that the available land has been dedicated to cars, and that makes cars very convenient. It isn't because cars are inherently convenient it's that we have spent unthinkable amounts of effort carving through hills, flattening rocks, stabilising mud, to make cars convenient. Because cars are expensive so it's good for car companies if lots of people buy them. One can't take an unbiased "fair" position, one must make choices - one can't sit on the fence between "it's important that people can get to home/social/work/shops in many ways" and "it's fine if cars are the only way and if that's a problem for some, tough".