As leaders of experienced, skilled and knowledgeable staff, we want team members to be able to speak up and disagree with something they don’t think is right. We want people to highlight the problem that no-one else has thought of.
However, a dissenting voice can be very disruptive when it goes against the goals, direction or well-being of a team. It’s especially destructive when this disagreement comes down to personal preference or an individual putting their own goals above those of the team. Some team members can be repeat offenders when it comes to disagreeing with an overriding team decision. If you are a team leader and those characters exist in your team, then you know who they are.
A disagreement can be about something as benign as whether or not to fix a low-priority bug, or as caustic as whether retrospective meetings are a valuable use of their time. Team leaders can sometimes feel unable or ill-equipped to challenge a strong individual’s dissenting opinion. They may be tempted to sit-back and hope that they quieten down or that the team’s consensus wins out. However, that kind of procrastination can lead to problems snowballing, a lowering of team morale and divisions forming within the team.
For the good of the team dissenting opinions should be noted and addressed as soon as possible. It can be tempting to make the incident less personal by bringing-up the disagreement in a team context like a sprint retrospective meeting – “I understand some of us think that this is a bad idea”. I think this is less effective, as the individual you are ultimately trying to reach can metaphorically opt-out of team discussions and decisions.
Instead, as soon as you notice a dissenting voice that has the potential to derail the team, I’d recommend taking the individual aside as soon as is feasible and having a private conversation. I’d probably structure the discussion something like this:
- Explain the situation; that the team have reached a consensus, or are tackling agreed goals, and you’ve noticed that (s)he disagrees.
- Reiterate why the team are doing what they are doing. Be open.
- Ask the individual to help you understand why they disagree.
- Discuss the impact this disagreement could have on the team and its success.
- Ask the individual what they can do to move forward. Can they agree to get behind the decision of the team or team leader? Perhaps they can raise their ideas more constructively?
Asking the dissenter what they can ‘do’ about the problem is a vital part of the conversation but can often best missed. By asking, you put the onus on the individual to improve the situation and make it quite clear that there needs to be a change. This isn’t always a comfortable discussion, which is why it is tempting to avoid it. However, by tackling the problem head-on leaders can nip team dysfunction in the bud and protect goals and morale.
Leading Agile Teams 
Speaking as an occasional dissenter (“your usual cantankerous self” as someone put it recently), you (as the manager) need not aim to get my agreement in these situations.
(Quoting from http://getmespark.com/wp-content/uploads/RiskStrategyImplementation.pdf) ‘It’s not “agreement” that will get everyone behind your decision; it’s combining shared understanding with commitment. If the whole group deeply understands where they disagree and why they disagree, and at the same time can generate a very high level of commitment to the decision, then you’ve achieved consensus.’
What’s important to me is to know that my views were properly heard and considered, and to understand the reasons the group made the choice they did. I respect the wisdom of my peer group and will go along with their decision, but to gain my active support they need to have shown reciprocal respect for me.
Of course I’m assuming that the dissent relates to the issue being discussed – you mentioned the possibility of an underlying personal agenda. That certainly happens, but if the dissenter has rational, scientific inclinations (if they’re a software engineer, for example) you might be mistaken when you perceive a link between their position on this issue and that agenda.
One final point: other members of the team can help, particularly if they are neutral on the issue themselves. We logical-thinking engineers may consider a statement like “I can see merits on both sides …” as a worthless way to enter the discussion; we may prefer to sit back and wait for reason to prevail. But actually I think helping either side to understand the other (using facilitation skills) is a good way for a less opinionated person to make a valuable contribution.