It is hard enough getting initiatives delivered in business without have to deal with people constantly telling you about all the things that might go wrong, or about why your initiative won't work. Ignore these people at your peril.
Larger organisations are particularly prone to "groupthink" because of hierarchical management structures. Employees are usually expected to do what their boss tells them to do. This leads to frequent water cooler discussions along the lines of; "I've just been asked by my boss to do x, it is madness / will never work". Some high profile examples of groupthink leading to disaster include the Deepwater Horizon oil spill where there were a number of individuals who had pointed out specific risks with the set up. These were ignored because they were following "best practice".
Dissenters don't have that conversation at the water cooler, they tell their boss why they think it is a bad idea. A stock response for the lazy manager in this situation is "bring me solutions not problems". The smarter manager by contrast will listen and try to properly understand why the dissenter thinks that the initiative is a bad idea and possible make changes as a result.
You need to distinguish between a dissenter and a moaner. Some people are never happy about any new initiative because it involves change which can be extra work for them. These people are moaners and need a different kind of management. Dissenters usually have specific knowledge and insight which drives their behaviour. They can come from any part of the organisation or even outside (e.g. customers, suppliers). Their knowledge or insight is usually related to how things work on the ground or the particular quirks of a customer or supplier. Sometimes this is expressed as unease initially, but becomes more vocal once they have had a chance to think about it.
Successful organisations embrace dissent because it does three things. Firstly, it drives a process of natural selection for ideas. Strong ideas stand up to dissent weak ones don't so dissenters offer a good test before money has been spent. Sometimes small tweaks to an idea make it much stronger and turn the biggest dissenters into the biggest advocates.
Secondly, dissenters force everyone else to take a position on an initiative. This breaks the cycle of group think and encourages everyone to be more critical of the idea which then refines the idea and irons out more flaws.
Thirdly, dissenters help you to understand the risks and benefits of the initiative more clearly. If the initiative is developing a new product for example, they can help you to understand the limitations and also potential additional benefits if some changes are made.
So next time you hear yourself saying "bring me solutions not problems" pause for a moment to see if you are talking to a dissenter and if you are, maybe you need to listen.