What was the problem with eating food sacrificed to idols?

1 Corinthians 8:9-13 (NIV): >Be careful, however, that the exercise of your rights does not become a stumbling block to the weak. For if someone with a weak conscience sees you, with all your knowledge, eating in an idol’s temple, won’t that person be emboldened to eat what is sacrificed to idols? So this weak brother or sister, for whom Christ died, is destroyed by your knowledge. When you sin against them in this way and wound their weak conscience, you sin against Christ. Therefore, if what I eat causes my brother or sister to fall into sin, I will never eat meat again, so that I will not cause them to fall. It is clear that eating meat sacrificed to idols is not a sin. But it could lead other Christians to do so too, and as a result they would be destroyed? Or fall into sin? Is Paul implying that it will lead them into other sins? Or just that they will think they are sinning (when in fact they are not) and will feel bad, and we should be mindful of this? That they think that they will be destroyed (when in fact they won't be)? Why did Paul say these people have a weak conscience? Don't they have an over active conscience?