If the main reason you become a pastor is to promote some cause, then your soul is in danger, and so is the congregation's.
Being pastor of a congregation is hard work. I was one for 30 years. It’s not a day job. It's a vocation that takes up most of your waking hours.
A pastor's life and family are necessarily involved in their congregation “in season and out of season.” I often say being a pastor is the best vocation there is, but the worst job. If you are not called to it, you really don't want to do it.
When I started as a pastor, I learned quickly that you have to love your congregants, even the unlovable, of which there are far too many. These take up a good deal of your time. Some of them you will just never learn to love, and you have to turn them over to God, who does.
I had been a political activist in college and seminary, and had gone to jail for my causes, but when I got into the pastorate I learned very quickly that you can’t be a prophet until you have earned the peoples' trust. This means years of marrying and burying and sitting by hospital beds.
If you do this well they may be ready to hear hard truths from the pulpit. Or they may not. Certainly Isaiah’s prophecies fell on deaf ears.
New ministers who have grown up in the church have a leg up, because they know its rhythms and customs, its “grandeur and misery.” But today many of our ministerial candidates haven't grown up in the church. They often come to seminary in a process of self-discovery. Most of us did that to one degree or another. Seminary is a good place to learn many useful things. What seminaries are not so good at is forming men and women into Christians, much less teaching them how to be faithful pastors. Don’t blame seminaries. It’s not their job. Christian formation is primarily the church's job.
Many come to seminary not only to find themselves, but because of a passion for a social cause, which is fine. In seminary the flame of their passion is often fanned by others who share it, which is also fine.
But if all you know of the faith is what you learn in seminary, you are at a distinct disadvantage. And if the main reason you accept a call from a congregation is to promote your cause, then your soul is in danger, and so is the life of a congregation. The congregation you go to may or may not share your passion. It can be dangerous either way.
If they agree with most of your views, the temptation is to self-righteousness, a tendency to see sin and evil “out there” in your ideological adversaries, and not also in your own soul. Then you have lost the great insight expressed by the Reformers' wise axiom simul justus et peccator, that we are both justified and sinners. Some ministers risk this danger for their entire careers and they don’t even know it.
The other temptation is perhaps more dangerous: to go to a congregation where they don’t share your cause, and you scold them for it. You do not learn to love them, and they do not learn to love you, and eventually your ministry fails.
Some of our pastors sadly seek out this kind of martyrdom, and when they are inevitably cast out, they can then turn and say how stiff-necked and hard-hearted their congregation is. Congregations can be stiff-necked, hard-hearted and even abusive. This is nothing new. Read Exodus or First Corinthians.
But congregations can also be wonderful, supportive, gracious, and long-suffering, especially if they sense you are really trying to be their faithful pastor.
If you’ve the diligence and patience, you can be both a prophet and a pastor. But you’d better be a pastor to the people first. Because that is your primary calling.