The accusation of being a "bandwagon" fan is, in a sense, an attack of a person's loyalty and integrity in the area of sports fandom. What it's really communicating is that the said fan is not really a fan of the team, at all, but a person who like's the feeling of being on the side of a winning team. Loyal, or "die hard" fans despise those types of people because they're seen as opportunistic and shallow - the political equivalent of a person who claims to be willing to fight for the death to defend his country, who quickly changes his loyalties to the invading force when the tide of the battle turns. There's no loyalty at all, just self-centered opportunism.
There's a version of this in the Christian faith, as well. I think the book of Job captures the struggle of "fair weather worshipping" very well:
Then the Lord said to Satan, “Have you considered my servant Job? There is no one on earth like him; he is blameless and upright, a man who fears God and shuns evil.”
“Does Job fear God for nothing?” Satan replied. “Have you not put a hedge around him and his household and everything he has? You have blessed the work of his hands, so that his flocks and herds are spread throughout the land. But now stretch out your hand and strike everything he has, and he will surely curse you to your face.” - Job 1:8-11
Satan's pretty much accusing Job of being a "bandwagon" follower of God. The accusation which Satan lays out against Job is pretty much the same: Job is a self-centered opportunist who follows and worships God purely out of material self-interest. He's rich, the work of his hands if fruitful and successful and his family is healthy and happy. Given those circumstances, why wouldn't he love being a God follower? It's a fair question.
What follows this passage is Job being put to the test, with many of the happy, happy, joy, joy aspects of his life suddenly becoming bitter as he encounters tragedy after tragedy. And while his circumstances make a 180-degree turn and he mourns and laments openly, he does not (as Satan had suspected) curse or reject God.
It's a good lesson for us. What is my response when life isn't going swimmingly? Does a couple who struggles getting pregnant fume that God doesn't exist and their prayers are wasted? Does a young lady who has constantly encountered failed prospective relationship after another curse a God who she is now convinced wants her to live alone and miserable? Does one lash out bitterly when a potential exciting job prospect fail to materialize? These are perhaps easy answers in theory, but they are much more difficult in practice. I can empathize with the last example, which I experienced this past week.
I understand that disappointment and appreciating God's sovereignty has a major "head knowledge / heart knowledge" gap. I understand that well-intentioned Christian clichés (e.g. "God is in control", "God will redeem this", "God's greatest mercies are often things he withholds", "God will never refuse you the very best thing."), while true, often range somewhere between unhelpful and irritating. I understand, because I've been on the receiving end of these words, the giving end of these words, and both, when I've preached these words to myself. But the reality is that those words are true. It just takes the heart a long time to catch up to that.
Going back to sports references, there are many cynical people who hate when Christian athletes open post-game victory interviews, "First of all, I'd like to thank my Lord and Savior Jesus Christ...." The snarky retort of these detractors is, "What if they had lost? Would they still give thanks to Jesus?" My response is that I hope they would, because thanking God and worshipping and following Jesus aren't dependent on circumstances, it's a condition of grace which transcends circumstance.
I don't want to be "fair weather" worshipper of God. I don't want to be a "bandwagon" Christian. Difficult and hard circumstances shouldn't turn me from Him; if anything, they should make me cling harder. The ironic truth of the matter is if we really believe in God's goodness and sovereignty, the wise Christian will ultimately not jump off the bandwagon... because eventually things will work for the good for those who love Him and are called according to His purpose.