You do have point here and yeah, that is the problem with analogies etc they are an attempt at parallel, but certainly not exacting. But I do think you make a good point in that there is more freedom and the ability to really select and put one's feet to the fire, when one is talking about party loyalty.
It is up to us the voters to put those feet to the fire. It is up to us to vote someone out or in and even to put pressure on them and other candidates in our party, when we feel they are not doing the job we sent the there to do.
I see this as a good thing. I see this as an example of why participation in a political party is so important. It is not perfect and yes, there are times we can just shake our heads and go, "What the ?" But we can even more then with out family clearly define who is a member and who is not. As they say . . . you can't pick your family, but you can pick your FRiends :-).
So hey, I'll renege on my own initial analogy and move on to the next level. This to me is what we do in politics. Sometimes we have to reevaluate and make change and this we can do in our own political party. Thus us is them if we participate.
I must add though there is an expected certain amount of compromise in politics and one needs to really decide, both individually and as a group when to fight and when to voice and opinion and stand down.