I would say a few things:
1. MacArthur is biased against the Christian's consumption of alcohol in the first place.
2. Although we should be careful not to cause a brother to stumble, the weaker Brother (as it were) has a responsibility to grow in the grace and knowledge of the Lord Jesus Christ, which includes Christian Liberty.
3. Thus, I think one should abstain if he is going to offend the weaker brother by partaking of alcohol, but only insofar as the weaker brother is ignorant of the concept of Christian Liberty.
4. If, at this point, the weaker brother is ignorant of a Christian's liberty concerning things indifferent, the stronger should gently teach the weaker Christian the truth of such.
5. After exposure to the concept of Christian liberty, as found in the Scriptures, if the weaker brother persists in acting offended, etc., although the stronger brother should still be sensitive, he need not feel the need to hide his partaking of things indifferent because the weaker brother's objection is no longer out of ignorance, but out of their own personal conviction they would desire to press on everyone else.
6. Ultimately, if things work out as I noted above, the stronger brother may not want to even drink on an outing with this weaker brother, because one must question how it would edify either the believer, or unbeliever, in any way. However, if the weaker brother says such a thing like, "We don't drink. We're Christians," it is my opinion that the stronger brother ought not let his good be spoken of as evil.
