On moral matters about which Gods word has spoken, the word is supreme. On matters that are morally neutral, and are not addressed then the overriding concern must be whether our actions will cause another to lose their connection with God, to stumble in their faith.
This does not include legalists who wish to impose their narrow-mined scruples on others. Such are not weak brothers, but willful brothers who glory in the subjection of others to their narrow beliefs or ignorance. This is tyranny, and as Christians we must always be on guard against this.
1 Cor 10:23
23 "All things are lawful," but not all things are helpful. "All things are lawful," but not all things build up.
1 Cor 6:12
12 "All things are lawful for me," but not all things are helpful. "All things are lawful for me," but I will not be controlled by anything.
The word lawful exestin: it is right (through the figurative idea of being out in public):
1 Cor 8:9
But take heed lest by any means this liberty of yours become a stumbling block to them that are weak.
Stumbling block, proskomma from; a stub. Literally this means anything laid in a man's path, over which he may fall. In the Scriptures, however, the word is used commonly in a figurative sense to denote anything which shall cause him to "sin," as sin is often represented by "falling;" see the note at Matt 5:29. And the passage means that we should resolve to act so as not "by any means" to be the occasion of leading our brethren into sin,
Let us not therefore judge one another any more: but judge this rather, that no man put a stumbling block or an occasion to fall in his brother's way. an occasion to fall skandalon ("scandal"); To Bend; a trap-stick (bent sapling), i.e. snare (figuratively, cause of sin):