What if the common ground isn't sin? Where in these topics does good meet sin. That is where we draw the line.
Christian Liberty... but be sensitive and loving to brothers first and foremost.
Romans
14:13 Let us not therefore judge one another any more: but judge this rather, that no man put a stumblingblock or an occasion to fall in [his] brother's way.
14:14 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.
14:15 But if thy brother be grieved with [thy] meat, now walkest thou not charitably. Destroy not him with thy meat, for whom Christ died.
14:16 Let not then your good be evil spoken of:
14:17 For the kingdom of God is not meat and drink; but righteousness, and peace, and joy in the Holy Ghost.
14:18 For he that in these things serveth Christ [is] acceptable to God, and approved of men.
14:19 Let us therefore follow after the things which make for peace, and things wherewith one may edify another.
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.
1 Corinthians
8:9
But take heed lest by any means this liberty of yours become a stumblingblock to them that are weak.
8:10 For if any man see thee which hast knowledge sit at meat in the idol's temple, shall not the conscience of him which is weak be emboldened to eat those things which are offered to idols;
8:11 And through thy knowledge shall the weak brother perish, for whom Christ died?
8:12 But when ye sin so against the brethren, and wound their weak conscience, ye sin against Christ.
8:13 Wherefore, if meat make my brother to offend, I will eat no flesh while the world standeth, lest I make my brother to offend.