Photo: National Transportation Safety BoardCross-posted from Natural Resources Defense Council. Proponents of the Keystone XL tar-sands pipeline are using a disingenuous argument to avoid further scrutiny of TransCanada's proposed pipeline. They argue that the concerns of landowners, farmers, and first responders regarding the safety of Keystone XL are unreasonable because TransCanada has agreed to 57 conditions suggested by pipeline safety regulators that will make it safer than other pipelines. There's a serious flaw with this argument -- most of the conditions TransCanada "voluntarily" agreed to are also the minimum standards that all pipeline operators must follow. Recently, Secretary of State …