Much like the old adage - there's no such thing as bad publicity - some would argue that no matter the motivation behind it, any form of environment-oriented communication is a good thing. Even if it is inaccurate. Unlike a celebrity seeking publicity, however, environmental issues do not just need attention, they need the right attention. It is risky to assume that any message which motivates people to support environmentalism is always positive, regardless of the accuracy of the information. The danger is that people may unknowingly do or buy things that they think are environmentally friendly, but in actuality are not. If people falsely believe they are living environmentally-conscious lifestyles they may be lulled into complacence about the true state of environmental issues.
A great example someone brought up in a debate recently, was the proliferation of "eco" shirts that proclaim an environmental message on a person's clothing. Ironically, these supposedly "green" shirts are often made from materials not produced organically or only a small percentage of their make-up involves an organic material. So people buy these shirts thinking they are purchasing environmentally-friendly clothing when they might actually be promoting the very environmentally-unfriendly practices they oppose.
In the case of environmental issues like global warming, toxic emissions, wildlife conservation/preservation, etc. false information is almost as bad as no information at all. These issues are not celebrities, they are real problems affecting the environment and human communities. If environmental messages do not accurately describe the situation, how will anyone be able to fix it?