Can demons or idols harm a Christian who eats meat that was sacrificed to them?
No, demons or idols cannot harm a Christian who eats meat sacrificed to them. Idolatrous gods have no power over a believer, so the meat can be eaten without worry. Yet if eating would cause a weaker Christian to stumble, it should be avoided for that person's sake.
Les explains that Paul never told these believers to stay away from a pagan wedding feast; they were free to go. Even though an idolater friend believes the meat had to be blessed and sacrificed to a pagan god to keep demons out, the believer is told not to worry, because those idolatrous gods cannot do anything to a believer. So the meat may be eaten. However, if a brand-new, immature Christian sees a mature believer eating and is caused to stumble, then for that young believer's sake, do not eat. As far as the idol having any power, forget it. The context also notes that pagan temple priests kept a portion of the sacrificed meat and gave the rest back to the individual, but that does not give the idol power over the believer.