Sorry, but read literally what you are claiming is totally acceptable and does not indicate that we shouldn't be using biofuels. You seem to be saying that biofuel generation including burning as fuel using a net positive amount of carbon. There is no reason it shouldn't. It is a viable strategy if it uses less than the fossil fuel alternative. Note that the way to measure the alternative here is not the emissions from burning a unit of fossil fuels, but that plus all the emissions involved in extracting, refining and transporting the fossil fuel. For example, this includes flaring (~1% of all global C02 emissions).

It would even be viable if the total amount of carbon generated by the farming, processing and transportation of biofuels without including burning but subtracting the carbon taken from the air by plant growth, was a net positive by itself, as long as the excess was less than the corresponding total for fossil fuel production, including all the carbon involved in its production.

I accept the validity of what you said about land use in the sister thread, but I don't think you've established that this criterion isn't true (and making the much weaker claim above suggests that you aren't able to).

I also believe that many types of impact on the environment (for example what you mentioned about topsoil and water quality) should be treated with much lower priority than the greenhouse effect. If biofuels, or some other strategy for reducing emissions such as solar or wind power generation has a devastating but localized impact on some ecosystems, it might be worth it to forestall the wider effects of global warming. This is a matter of opinion though, and I do not live in an area which could be sacrificial in this sense.