No. Legalism is the error of abandoning our liberty in Christ in order to take on a yoke of legal bondage (Galatians 5:1). There are actually two kinds of legalism.
First is the one recognized and despised even by the fundamentalist with his thick rule-book. It's the legalism of the Judaizers. The Judaizers wanted to make circumcision a requirement for salvation. They had fatally corrupted the gospel by adding a human work as a requirement for salvation. That is certainly the worst variety of legalism, because it destroys the doctrine of justification by faith and thereby sets up "a gospel contrary to the one you received" (Galatians 1:8-9).
But another kind of legalism is the legalism of the Pharisees. It's the tendency to reduce every believer's duty to a list of rules. This is the kind of legalism that often seems to surface in our comment-threads. At its root is a belief that holiness is achieved by legal means—by following a list of "standards." This type of legalism doesn't necessarily destroy the doctrine of justification like the legalism of the Judaizers. But it does destroy the doctrine of sanctification, and it is certainly appropriate to call it what it is: legalism—i.e., a sinful misapplication of law; an attempt to make law do work that only grace can do. Like the Judaizers' brand of legalism, it brings people under a yoke of bondage Scripture has not placed on them.
That is precisely what happened in the fundamentalist movement, and one of the major reasons that movement has failed so notoriously. Legalism diverts people's attention from sound doctrine, so that the typical fighting-fundie legalist is doctrinally ignorant, reserving his or her "convictions" for a silly man-made system of rules. Ask the typical self-styled fundamentalist to define the difference between imputed and imparted righteousness, and he will not be able to do so. Suggest that it's OK for women to wear pants, or for people to use another version besides the KJV for Bible study, and the same fundy will lock and load his angry dogmatism, ready to do battle or even die for some ridiculous man-made "standard." Thus, as Jesus said, they have nullified the Word of God for the sake of their man-made traditions.
Let me say this plainly: It is a sin to impose on others any "spiritual" standard that has no biblical basis. When God gave the law to Israel, He told them, "You shall not add to the word that I command you, nor take from it, that you may keep the commandments of the LORD your God that I command you" (Deuteronomy 4:2). And, "Everything that I command you, you shall be careful to do. You shall not add to it or take from it" (Deuteronomy 12:32).
If we add rules that Scripture doesn't make—especially if we try to impose our man-made rules on other people's consciences as a standard of spirituality—we are guilty of the same sin as the Pharisees and worthy of the same harsh rebukes Christ leveled at them.