True legalism is observing the letter of the law over the spirit of the law, it has no room for compassion. Compassion and convenience are not two sides of the same coin. Whereas compassion makes room for a person to succeed or fail, therefore it has its limits, convenience is pandering (giving in) to the desires of another, 1 John 2:4.
Room to fail implies that at some point the letter of the law must be applied or else there is no law or order (anything goes). No grammar (order) no language.
The word “legalism” is not found in the Bible. It is a term used to describe the attempt to change the Gospel message, whether intentional or not. The idea originally was that Gentile believers needed to become Jewish to be saved, Acts 15:1-5. The first council in Jerusalem did away with that idea (Acts 6-29), but extremists kept pushing it in churches wherever Paul went.
Today it has morphed into what some call a system of behavior required of believers that determine whether a believer is a believer or not or “traditionalism”. But, Paul emphasizes the value of maintaining right traditions, 1 Corinthians 11:2 and 2 Thessalonians 2:15.
When Jesus spoke concerning traditions He was talking about the distortion of the Mosaic Law by some. Those distortions canceled out the purpose and function of the Law, Matthew 15:3-6. Paul supported this same idea in Colossians 2:8.
During the 400 silent years (when there was no prophet of the Lord speaking) the Jews developed a body of interpretation of the 39 OT books called the Talmud. These were interpretations or practical applications of the Mosaic Law in day-today living. The problem with the Talmud was that it became easy to manipulate by those in power over the people.
When Jesus spoke about the traditions of the Pharisees and Saducees the Talmud is what He was talking about.
The church needs to always be ready to respond to any question posed concerning our traditions whether it concerns doctrine (what we believe) or practice (how we apply what we believe). The problem comes when we disagree with an interpretation and therefore an application of what we believe.
Now there are some doctrines where we can all agree to disagree, such as with eschatology but never with Soteriology. Worship styles are one of those areas where we tend to put the cart before the horse, as it were. What I mean is that in an attempt to attract more or new people to a worship service we make a change, which some see as lowering a standard of sanctification. So, those who resist the change are called legalists, unwilling to change because of tradition (what is old and in the past). At the same time those who want change become equally as resistant to compromise between the two views.
My concern is that this argument causes us to appear petty in the eyes of the world to which we are trying to witness. Changes in style are always fine as long as we are careful to avoid the appearance of worldliness or paganism, which was the error of Jeroboam, 1 Kings 12:25-33 and Balaam, Numbers 22-24, 2 Peter 2:15, Revelation 2:14.