It is extremely common to have disagreements while working to implement an idea at a startup. This makes it so important for the small team to get along and feel comfortable thinking outside of the box toward successful implementation of the idea. Disagreements are a given at this stage of the company, and they should be embraced. Why does this happen? It happens because ideas have no substance at all. They're just ideas.
Think of what an idea is. It is the antithesis of a formulated system. A proven business model, scientific method, or proven hypothesis has gone through hundreds or thousands of iterations, tests, proofs, mistakes and implementations. An idea is pre-seed, and startup is just the seed itself. There's nothing there except the idea. It hasn't been proven, and it hasn't been tested.
Even if my partner and I both have a similar vision, a similar dream of a disruptive technology, "our" idea must be developed, germinated, proven and implemented. This process requires discussion, give and take, and most often disagreement. But, if everyone working on the implementation of the idea understands this, the disagreements become part of the process. They are embraced as part of the fun. Comments like: "That's wrong," "We shouldn't do it that way," and "That makes no sense," instead morph into, "That's interesting," "I didn't look at it that way," and "That's brilliant!" All ideas are embraced, until direction becomes clear. In fact, by embracing and being open to a different perspective of the idea, even if the entrepreneur doesn't initially agree with it, often times that exact idea becomes a clear guiding light, just days later.
With the startup, we don't know where the idea will go. We don't know all of the factors influencing the probability of success of the idea's implementation. It's just.... an idea.
So, positive, creativity, fun, team, a bit of luck, and a ton of work is the name of the game. And, if you love the people around you, as the implementation of the idea becomes reality, disagreement becomes part of the game also. And, if all of those ingredients are mixed in and accepted, it just doesn't seem like work anymore. It's all creativity and fun.