Passionate unity can be a beautiful thing, or it can be a horrific evil. Thus, one thing is certain: passion, by itself, does not determine the quality of any unity. Men can be passionate and unified about a number of things. In Acts 19 we read about the passionate chanting of the inhabitants of Ephesus, where they declared "Great is Artemis of the Ephesians" for two hours.
Now that's passion!
But it also happens to be great idolatry. Without truth, our passions remain unsanctified, being defiled by our indwelling sin. But there is something about our human nature that wants to herald passion (even sincere passion) as that which is commendable (apart from truth), but I would suggest to the reader that such thinking is dangerous. The inhabitants of Ephesus may have been very sincere in their devotion to Artemis, but this did not sanctify their idolatry. Any unity among men cannot be adjudicated by the substance of raw enthusiasm alone; instead, truth stands as the plumb line for any alliance and determines if such unity is holy or unholy. We see this very clearly illustrated through the Greek word homothumadon - "one accord" - a word that speaks of a passionate unity among men, whether good or bad:
Romans 15:5-6: 5. Now may the God who gives perseverance and encouragement grant you to be of the same mind with one another according to Christ Jesus, 6. so that with one accord [homothumadon] you may with one voice glorify the God and Father of our Lord Jesus Christ.
Acts 18:12-13: 12. But while Gallio was proconsul of Achaia, the Jews with one accord [homothumadon] rose up against Paul and brought him before the judgment seat, 13. saying, “This man persuades men to worship God contrary to the law.”
The simple construct of this word - homothumadon - is quite telling: homo [same] + thumadon [from thumos - passion]. Overall, it speaks of a unity that is rooted in a common passion and resultant conviction among men. What this term does not settle is the basis of such passion/unity, and therefore, context is essential and determinative. As revealed in Romans 15:5-6, the Christian's passionate unity [v.6] is rooted in a like-mindedness that is in Christ [v.5]. Without such like-mindedness in Christ, our unity is anchorless, no matter how passionate it may be. This is evident in Acts 18:12-13. Those Jews who sought to try Paul before Gallio were extremely unified and passionate about their cause, but we must remember the shallowness of such zeal:
Romans 10:1-2: 1. Brethren, my heart’s desire and my prayer to God for them is for their salvation. 2. For I testify about them that they have a zeal for God, but not in accordance with knowledge.
Without truth, all zeal is rendered is useless. This should remind us of the danger of subjectivism, where the worshipper's personal affections are elevated above God's truth. Zeal is crucial indeed, but without truth, it is wasted energy. The other extreme offers no solution either: truth, without genuine faith, hope, and love is nothing less than religious hypocrisy.
This lesson of genuine unity is crucial, because the extremes of men (Subjectivism or Pharisaism) offer us no hope. The biblical path is the true path. Therefore the church must seek a passionate unity that is founded upon nothing else but the stable foundation of God’s Word.
 The thumos in which the unanimity consists may be anger (Philo Flaccum, 144), fear (Jdt. 15:2), gratitude (Wis. 10:20), etc. Theological dictionary of the New Testament. 1964-c1976. Vols. 5-9 edited by Gerhard Friedrich. Vol. 10 compiled by Ronald Pitkin. (G. Kittel, G. W. Bromiley & G. Friedrich, Ed.) (electronic ed.) (5:185). Grand Rapids, MI: Eerdmans.