1. There is no condemnation for anyone who is in Christ Jesus. Romans 8:1
2. To the pure, all things are pure, but to the defiled and unbelieving, nothing is pure; but both their minds and their consciences... Titus 1:15
3. It is not what goes into the mouth of a man that makes him unclean and defiled, but what comes out of the mouth; this makes a man unclean and defiles [him]. Matthew 15:11.
4. Also, (this really clinches it, in my opinion) Romans 14:14-23 says:

14 I know and am persuaded in the Lord Jesus that nothing is unclean in itself, but it is unclean for anyone who thinks it unclean. 15 For if your brother is grieved by what you eat, you are no longer walking in love. By what you eat, do not destroy the one for whom Christ died. 16 So do not let what you regard as good be spoken of as evil. 17 For the kingdom of God is not a matter of eating and drinking but of righteousness and peace and joy in the Holy Spirit. 18 Whoever thus serves Christ is acceptable to God and approved by men. 19 So then let us pursue what makes for peace and for mutual upbuilding.
20 Do not, for the sake of food, destroy the work of God. Everything is indeed clean, but it is wrong for anyone to make another stumble by what he eats. 21 It is good not to eat meat or drink wine or do anything that causes your brother to stumble.[c] 22 The faith that you have, keep between yourself and God. Blessed is the one who has no reason to pass judgment on himself for what he approves. 23 But whoever has doubts is condemned if he eats, because the eating is not from faith. For whatever does not proceed from faith is sin.

1. There is no condemnation for anyone who is in Christ Jesus. Romans 8:1
2. To the pure, all things are pure, but to the defiled and unbelieving, nothing is pure; but both their minds and their consciences... Titus 1:15
3. Also, (this really clinches it, in my opinion) Romans 14:14-23 says:

14 I know and am persuaded in the Lord Jesus that nothing is unclean in itself, but it is unclean for anyone who thinks it unclean. 15 For if your brother is grieved by what you eat, you are no longer walking in love. By what you eat, do not destroy the one for whom Christ died. 16 So do not let what you regard as good be spoken of as evil. 17 For the kingdom of God is not a matter of eating and drinking but of righteousness and peace and joy in the Holy Spirit. 18 Whoever thus serves Christ is acceptable to God and approved by men. 19 So then let us pursue what makes for peace and for mutual upbuilding.
20 Do not, for the sake of food, destroy the work of God. Everything is indeed clean, but it is wrong for anyone to make another stumble by what he eats. 21 It is good not to eat meat or drink wine or do anything that causes your brother to stumble.[c] 22 The faith that you have, keep between yourself and God. Blessed is the one who has no reason to pass judgment on himself for what he approves. 23 But whoever has doubts is condemned if he eats, because the eating is not from faith. For whatever does not proceed from faith is sin.