Our number one goal is to bring about change. Any campaign that scares off potential supporters and marginalises the remainder is counter-productive. We have to start thinking in the short terms and practical realities that politicians are forced to consider.
1. Meat is Murder.
We certainly have to look at reducing meat content in our diets, but calling for global veganism is too extreme and attacks the generality when it is the specifics that matter. We have to move away from intensive farming to a more labour-intensive organic system, and that means rearing animals in a natural way with a varied diet so they can fertilise the land they live on and bind up large volumes of carbon in the soils.
Often the best way of looking at the problem is to figure out why a particular activity leads to large emissions. With meat-eating, it's because the volumes we demand lead to factory farming. Do away with factory farming, then adjust your meat intake to match production in less intensive ways. Reducing population will allow significant meat content without harming the atmosphere.
One must also consider that, within the carbon cycle, biomass is just biomass, no matter what form it takes. Any animals that exist will produce methane and CO2, and even if they are part of a manmade/managed ecosystem, they are still a part of the natural cycle of carbon and do not add anything man-made. Those animals that are extracted from anything that might be called an ecosystem and reared artificially, however, are extraneous to the natural cycle, and their emissions should be eliminated.
2. All Cars are Bad
Again the target is wrong. We have to stop burning fossil fuels to make and power cars, and reuse/recycle every part they contain. A car is not inherently wrong. We just have to make their manufacture and use low- to zero-impact.
3. Evil King Coal.
Burning coal should be phased out as rapidly as possible - except in those rare instances where using coal has no significant impact on the environment. Coal can be used for a large number of things, just so long as none of its by-products from use are released into the atmosphere.
Take, for example, plastics and carbon nanotubes (and this holds true for all fossil fuels). They require long-chain hydrocarbons for efficient manufacture. They often incorporate molecular structures that would be poisonous if set free in the world. But plastics are frequently the most stable forms of carbon sequestration there is. When Oil peaks, it's not just the price of fuel that will sky-rocket (as it did last summer). The price of everything that uses oil as a feedstock will go through the roof too.
We might also consider a campaign against biodegradable plastics. Burying megatonnes of plastic deep in the ground where it will remain indefinitely is one way to sequester fossil carbon more or less permanently and avoid it turning to methane.
4. Too Many Children.
Population control happens anyway - there's no need to campaign for it. In any country where women are educated and have ready access to contraception, fertility rates fall - ultimately to below 2.1 per couple, which is the level for sustained population. Most of Europe, Japan and North America are already below this rate and worrying increasingly about demographics - with a falling number of workers supporting a rising number of pension-welfare dependants.
So climate campaigners can join the existing, highly positive campaign, and keep quiet about their reasons. Campaign vigorously for universal primary education for girls (as well as boys), and for family planning clinics throughout the third world. Oppose those who object to any form of effective contraception. Encourage healthcare for children so that their parents do not think they need any 'spare capacity'.
Above all, remember that the enemy is not lifestyles, over consumption and wealth. The enemy is the wanton burning of fossil fuels and the lack of support for sustainable alternatives, coupled with unsustainable population growth caused by ignorance and lack of access to condoms or the pill.
The goal is to live in harmony with the world, taking what it can give, and give again the following year without any danger of running out.