"Why can't Catholics (or Christians in general) just let people live their lives the way they want to live them?"
THE CATHOLIC HTOWNER:
Let's get one thing out of the way about this question: out of all the people in the world, atheists are the LAST people who should be asking this question.
Because they have the WORST and most HYPOCRITICAL track record when it comes to this issue.
Think about it. In every society or country where atheists hold the key leadership positions, have they ever at any time let Catholics or any religious group worship or preach freely?
Of course not.
From the Red Army's invasion of Tibet, to the explosion of the Christ the Redeemer Cathedral in Russia, to current attacks now against anyone who dare defy the gay agenda, secularists and atheists have NEVER allowed religious people to say what they wanted or even tolerated religious people talking back to an atheist.
All this from a group who says religious people need to "be more open-minded" and "tolerant of other views", that "we live in a multi-cultural society" and "all faiths are the same anyway" and "you shouldn't impose your beliefs on others."
Strange...atheists don't seem to have any problem forcing their beliefs on others...often by the end of a gun barrel.
But back to the question at hand...why can't Catholics or Christians leave others alone?
Simple: error should not go unanswered.
You see, all followers of Christ are called to "be perfect, as your heavenly Father is perfect" (Matt 5:48) but since man is a fallible creature, we do make errors, albeit not the same ones or even at the same time. Sure, we may make every effort possible to avoid error, but every now and again, errors do get through and we do need correction. Atheists, whether they want to admit it or not, are in the same boat as their religious counter-parts.
Perfect examples here:
Would an atheist speak out on someone who says a triangle has four sides? What about if someone places an historical event in the wrong time frame? Would an atheist say nothing about this mistake? Of course not.
"But, wait," a vocal yet misguided atheist would say. "What you're talking about here are objective, provable facts. While we can find the definite answers to those, that's not true about morals, so you Christians have no right to say someone else is wrong on their morals."
I, as well as many other Catholics, call out the atheists on that objection, since we're not the ones who claim all is relative while holding something as objectively true...otherwise, all your claims can and will be dismissed as just opinions..and ill-informed ones at that.
Whatever reasons a person can come up with as to why they would never let people keep believing these two falsehoods, those are the exact same reasons Christians would never let people continue in their error.
Here's where I think the atheist's real beef is: it's not so much atheists object to exposing error or making a mistake; they just object to people exposing atheist errors. Any sane adult would face the error and conclude all contrary views to the discovered truth must be false but atheists seem unwilling or too ill-informed to do this.
That in the end is why a) Christians can't leave people alone when the people commit error, b) we will never leave the person in their error and c) we should never expected to leave the person in their error.
Christians admit there is such a thing as an absolute; atheist idiots do not.
THAT makes all the difference in this life and the next.
Take no part in the fruits of darkness, but instead expose them. -Eph 5:11