Yeah, because in our system of government, if the candidate you voted for doesn't win, you get nothing. The way our elections are run forces us to form two broad coalitions of people with several different sets of values, and then pits those two coalitions against each other. This does basically guarantee that almost nobody gets everything that they want, and it forces a lot of compromises, .
If you really are a single issue voter, and since you believe that Trump and Clinton both have some values at odds with liberal democracy, than it makes sense to vote third party. But something tells me that since you do have generally liberal values, that you probably care a lot about other issues that Clinton agrees with, and that perhaps you recognize that Clinton has more liberal democratic values than Trump. In that case, it's a mark of immaturity to throw a tantrum and not support the person who shares some of your values just because you didn't get everything you wanted.
If we're damned to hell, my pragmatism will if anything only get us there slower. Once Clinton got the nomination, there was zero chance or Bernie, or Jill Stein, or anyone else other than Trump or Clinton being president. You being upset about that and refusing to vote for Clinton or Trump did nothing to change the direction of the country.
I voted for Sanders in the primary, too, even though I'm registered to vote in New Jersey and by that point he had no chance of winning the nomination. I hoped that the strong voter turnout for Sanders would convince some democrats that they would have support from their constituents if they supported positions farther to the left. But it seems that the general election sent the message that you cannot rely on the support of Sanders voters unless you are as far left as Bernie Sanders, and that they will vilify you if you have any political platforms that deviate at all from theirs.
No system of democracy guarantees that every voice will be heard. You have to accept that sometimes people won't agree with you on everything, and that you will need to compromise with some of them in order to get some what you want. Otherwise, you remain outside the democratic system because, understandably, no one is willing to work with an uncompromising idealist who disagrees with them.