One person believes he may eat anything, while the weak person eats only vegetables.  Let not the one who eats despise the one who abstains, and let not the one who abstains pass judgment on the one who eats, for God has welcomed him. (ESV)
I have said that I could never live as a vegetarian. I know that there are people who are horrified at the idea of eating meat. I am slightly horrified at the idea of having a diet that does not allow meat. For me, none of this discussion has anything to do with what Paul is saying here. I am referring to personal preferences. Paul is talking about something very different.
There was a reason why there were people in the church who refused to eat meat. The meat that is being referred to here had been offered to idols before it was made available in the marketplace. Those who were "weak" in their faith could not conceive of eating meat that was sacrificed to idols. They viewed those who ate that meat as pagans. How could Christians eat that meat?
Those who were eating the meat that was sold at the marketplace believed that idols were not real. They did not feel that it mattered that people offered meat to idols because idols are dead, lifeless things. They felt that they were free in Christ Jesus to eat anything that they wanted, regardless of what someone had done to it before they bought it. How could weak people not understand that?
Paul says that the answer is not judgment, but rather love. The "strong" should love the weak instead of forcing them to eat meat. The "weak" should not view the strong heretics, but simply love them even though they disagreed. There are issues in the Church today that we should use Paul's instruction for. We should be quick to love and slow to judge.
What issue in the church would cause you to view someone who disagrees with you as weak? In what way do you need to offer love to someone you disagree with, instead of judgment?