I've been involved in a discussion with a pastor on the topic of the "Weaker Brother" in Romans 14. We are on two different sides of the "Weaker Brother" brother debate. In his opinion, "Weaker Brothers" are mostly legalists, and most of the people who argue from the "Weaker Brother" perspective are legalists.
Are some people who use the 'weaker brother' argument legalists? Possibly.
Although, Paul used it and he was the most anti-legalist I can think of.
Is the 'weaker brother' Paul is talking about in Romans 14 a legalist? Absolutely not!
In scripture, legalists are the Pharisees, the Galatian Judiazers, or the older brother in Luke 15. They are almost always the prideful, "stronger" brothers or sisters.
Rather, Paul describes weaker brothers as tender souls who are entrusted to the care of the shepherds of the church in Rome.
In Romans14, Paul was exhorting those of stronger faith to not exercise their Christian liberty in a way that would cause those of weaker conscience to sin - don't flaunt your freedom.
This matter of exercising Christian liberty was NOT about proving wrong a bunch of legalists who were trying to impose their viewpoints on a bunch of young, idealistic pastors in the emerging New Testament church.
This was the well-seasoned, mature, founder of many early churches, Paul, looking out for new converts from a Gentile culture, riddled with extreme idol worship, passing into the holy communion of Christ-worshipping believers.
While I'm quite sure that converts from Judaism in Paul's day (much like the millennial/ emerging pastors of today who are rebelling against the legalism of fundamentalist churches), would have greatly desired to celebrate their liberty in Christ, Paul is pretty up front about how and why those of stronger faith should not give occassion for more tender believers to sin.
Paul also does not state, as some are inclined to believe, that we should 'teach Christian liberty' to weaker believers. While the knowledge and understanding of who we are in Christ can release us from false beliefs, it in no way validates teaching moderation when it comes to matters of conscience, which would amount to giving license to sin.
Those believers who have offered themselves as living sacrifices, to be transformed by the renewing of their minds, and to no longer be conformed to the pattern of this world, have no need for moderation. And let's not forget, leaders will be held to a higher account.
Meanwhile, I grant, those of us concerned for our newer or more tender of faith members should be gracious toward stronger brothers or sisters whose consciences are not as seared and wounded from being immersed so much in worldly ways. And we cannot allow the 'weaker' brothers and sisters to believe that their righteousness rests in abstaining from that certain thing about which they are convicted.
In either case, it seems fairly clear that the principle take away from Romans 14 is that love takes precedence over personal liberty (guarding against legalism is not Paul's point at all here).