For one believeth that he may eat all things: another, who is weak, eateth herbs.
Let not him that eateth despise him that eateth not; and let not him which eateth not judge him that eateth: for God hath received him.
One man esteemeth one day above another: another esteemeth every day alike. Let every man be fully persuaded in his own mind.
I know, and am persuaded by the Lord Jesus, that there is nothing unclean of itself: but to him that esteemeth any thing to be unclean, to him it is unclean.
But if thy brother be grieved with thy meat, now walkest thou not charitably. Destroy not him with thy meat, for whom Christ died.

COMMENTARY

Let not him that eateth despise him that eateth not; and let not him which eateth not judge him that eateth
One man esteemeth one day above another: another esteemeth every day alike. Let every man be fully persuaded in his own mind.
Any moral code is going to stipulate some actions as being worthy and others as unworthy. This is not only true of the moral codes within organized religion, even a rubric as vague as “what’s currently trending in society” still advocates for certain behaviors over others. Of course, different moral codes will disagree with one another as to which actions are worthy and which are not.
Proponents of these different moral beliefs often waste a lot of time arguing their points to those that do not even subscribe to the same tenets. Because each side values entirely different criteria, the vast majority of these debates are completely pointless, destined to generate aggravation, not understanding.
Why don’t we take Paul’s advice? Let us maintain the code we truly believe in, and let others do the same. We do not have to demand that everyone else agree with us, only that they be sincere in their own morals.

But if thy brother be grieved with thy meat, now walkest thou not charitably. Destroy not him with thy meat, for whom Christ died.
Tolerating another’s beliefs is good, but we can also take it a step further. Paul points out that we can take special care to not step on that which is sacred to others. Even if we don’t agree with all of their restrictions, we can govern ourselves by them while in their presence.
One does not even need to be religious do this, only socially polite. Those with vices still often put their cigarette out around non-smokers, choose jokes that don’t offend any present demographic, and avoid swearing around children.
Paul isn’t trying to tell us to be disingenuous, he simply wants us to be courteous.