The best way to answer this question is by citing the appropriate Scripture...
Romans
14:20 For meat destroy not the work of God.
All things indeed [are] pure; but [it is] evil for that man who eateth with offence.
14:21 [It is] good neither to eat flesh, nor to drink wine, nor [any thing] whereby thy brother stumbleth, or is offended, or is made weak.
14:22 Hast thou faith? have [it] to thyself before God. Happy [is] he that condemneth not himself in that thing which he alloweth.
14:23 And
he that doubteth is damned if he eat, because [he eateth] not of faith: for whatsoever [is] not of faith is sin.
Some probably suppose that this is talking about grape juice as well?