Heresy
The idea that your fellow man can accuse you of heresy has led to persecution and death in the past (
for example), which isn't a good thing. Only God can determine if a person is saved or lost.
We are warned that persecution and death will happen again.
Matthew 24:9 Then shall they deliver you up to be afflicted, and shall kill you: and ye shall be hated of all nations for my name's sake.
Revelation 13:15 And he had power to give life unto the image of the beast, that the image of the beast should both speak, and cause that as many as would not worship the image of the beast should be killed.
Tradition
Paul was positive about holding to tradition. The context being, "by word, or
our epistle."
2 Thessalonians 2:15 Therefore, brethren, stand fast, and hold the traditions which ye have been taught, whether by word, or our epistle.
Is Paul giving authority to a future power, or pointing to the existing authority in his day (Jesus, the apostles, the law and the prophets)? Or is it both? Regardless...
Paul also warned about tradition.
Colossians 2:8 Beware lest any man spoil you through philosophy and vain deceit, after the tradition of men, after the rudiments of the world, and not after Christ.
Jesus to the scribes and Pharisees, concerning tradition.
Matthew 15:1-6 Then came to Jesus scribes and Pharisees, which were of Jerusalem, saying, Why do thy disciples transgress the tradition of the elders? for they wash not their hands when they eat bread. But he answered and said unto them, Why do ye also transgress the commandment of God by your tradition? For God commanded, saying, Honour thy father and mother: and, He that curseth father or mother, let him die the death. But ye say, Whosoever shall say to his father or his mother, It is a gift, by whatsoever thou mightest be profited by me; And honour not his father or his mother, he shall be free. Thus have ye made the commandment of God of none effect by your tradition.
Paul gives a prophetic warning.
2 Thessalonians 2:1-7 Now we beseech you, brethren, by the coming of our Lord Jesus Christ, and by our gathering together unto him, That ye be not soon shaken in mind, or be troubled, neither by spirit, nor by word, nor by letter as from us, as that the day of Christ is at hand. Let no man deceive you by any means: for that day shall not come, except there come a falling away first, and that man of sin be revealed, the son of perdition; Who opposeth and exalteth himself above all that is called God, or that is worshipped; so that he as God sitteth in the temple of God, shewing himself that he is God. Remember ye not, that, when I was yet with you, I told you these things? And now ye know what withholdeth that he might be revealed in his time. For the mystery of iniquity doth already work: only he who now letteth will let, until he be taken out of the way.
Jesus warns us.
Matthew 24:4-5 And Jesus answered and said unto them, Take heed that no man deceive you. For many shall come in my name, saying, I am Christ; and shall deceive many.
Matthew 24:11 And many false prophets shall rise, and shall deceive many.
Matthew 24:24: For there shall arise false Christs, and false prophets, and shall shew great signs and wonders; insomuch that, if it were possible, they shall deceive the very elect.
We are repeatedly told to not be deceived; the onus is given to the individual to make a determination (through study of scripture, with the prayerful help of the Holy Spirit).
2 Timothy 2:14-16 Of these things put them in remembrance, charging them before the Lord that they strive not about words to no profit, but to the subverting of the hearers. Study to shew thyself approved unto God, a workman that needeth not to be ashamed, rightly dividing the word of truth. But shun profane and vain babblings: for they will increase unto more ungodliness.
I'm not arguing against tradition. Tradition can be a good thing. My own church has tradition. However, we are given the individual authority to discern what the truth is (through study of scripture, with the prayerful help of the Holy Spirit), and we should exercise it.
1 Thessalonians 5:21 Prove all things; hold fast that which is good.