Yes, I agree about undecideds -- but there are very few people who are undecided between Clinton and Trump. My point is that a lot of Sanders supporters are like me: that they won't convert to Clinton supporters does not mean that Sanders was a spoiler with regards to them. Sanders did not cost Clinton those votes. She never had them in the first place.

But, personally, the fear of the spoiler is just a "lesser of two evils" argument, and is one of the mechanisms by which the two major parties ensure that the status quo is maintained and there can never be a viable third party that might be able to give us some real alternatives. It's part of the systemic corruption of the system, and I think that falling into it just ensures that the major problems with the system will never actually be addressed.

I do understand exactly where you're coming from. I used to think similarly.