I have found online a quotation, which is widely attributed to Martin Luther but seems in fact to come from a 19th century novel about the reformation (which may be found in full here, although I have not tried).
If I profess with loudest voice and clearest exposition every portion of the truth of God except that little point which the world and the Devil are at that moment attacking, I am not confessing Christ, however boldly I may be professing Christ. Where the battle rages, there the loyalty of the soldier is proved, and to be steady on all the battlefield besides, is mere flight and disgrace if he flinches at that point.
This is well said, regardless of the fact that Luther did not say it.
The “little point which the world and the Devil are at that moment attacking” varies from time to time. In antiquity it was the question of sacrificing to Caesar’s genius — “just a puff of incense”, the persecutor would cajole. Many a temptation looks tiny from the outside. “The first one’s free…”
One you have sacrificed, or done whatever other thing you know to be wrong, of course, suddenly it’s different. That was suddenly a big step. No way back. Oh no. Nor is that just the trick of the persecutor. That is how human psychology works. It’s hard to find a way back, to bounce back. That’s why the Chinese torturers in the Korean War tried to trick POW’s into signing some ‘confession’ or other, as part of the brainwashing process.
The particular “little point” which the irrational world demands of the Christian is different today. But the modus operandi is the same. They create some artificial demand, and then insist on it. They pretend that it is really unimportant, but talk of nothing else except how bigoted Christians are for not complying, how unpatriotic, how hateful, how …. well, use your own adjective.
Worth remembering, the next time one of the stooges jeeringly “asks” why Christians are obsessed with sex, or homosexuality, or whatever evil they are promoting.