There's a tendency to think that compromise is always good, that there are always two sides to a story and the truth lies somewhere in between. I've blogged already on whether we have to listen to both sides before forming an opinion (see here). The short of it is that we don't. However, this doesn't imply that compromising between two extreme views isn't often better, only that we are not obligated to compromise.
So, the remaining possibility is that compromise may not be obligatory, but it is nonetheless better than alternatives. But why should that be so? There are certainly many obvious cases where compromise is highly irrational. 2+2=4, regardless of how "extreme" this position might seem. That is, we have a class of what might be called self-evident truths or axiomatic truths which should be adhered to regardless of considerations of compromise.
To these we can add a class of inter alia (or all things considered) claims which are carefully-articulated and -reasoned sets of judgements. Compromising on claims that one has already devoted a great deal of consideration to would require giving up something that one is convinced of, and has good reason for being convinced of. That is, if one has taken the time to articulate and defend a comprehensive universal healthcare policy, then one has an inter alia claim in hand: something that one can and should refuse to compromise on. (At least, without extremely good reason to change.)
In other words, it's not just the odd axiomatic cases where we can know with perfect confidence that we are right, but also the much more commonplace cases wherein a great weight of evidence has been marshalled in support of one's views. Which implies that it is only in the much-rarer cases where one is not sure what to believe that compromise is really a rational strategy.
Therefore, very often moderation and compromise are a result of lack of insight or depth of understanding. They are thus not good ends in themselves, but waypoints at which one can rest before gaining the ground necessary to support one's inter alia claims.