Over the years I have met many dear Adventists who feel that SDA ministers (and SDA's in general) should have nothing to do with ministers of other denominations. What's interesting is that this rigid view is one that church co-founder and prophetess Ellen G. White (the one whom many of these Adventists believe they are emulating) never advocated. Below are just a few quotations from Ellen White on the topic of SDA pastors interacting and working with non-SDA pastors.
—It should ever be manifest that we are reformers, but not bigots. When our laborers enter a new field, they should seek to become acquainted with the pastors of the several churches in the place. Much has been lost by neglecting to do this. If our ministers show themselves friendly and sociable, and do not act as if they were ashamed of the message they bear, it will have an excellent effect, and may give these pastors and their congregations favorable impressions of the truth. At any rate, it is right to give them a chance to be kind and favorable if they will.
Our laborers should be very careful not to give the impression that they are wolves stealing in to get the sheep, but should let the ministers understand their position and the object of their mission—to call the attention of the people to the truths of God’s Word. There are many of these which are dear to all Christians. Here is common ground, upon which we can meet people of other denominations; and in becoming acquainted with them we should dwell mostly upon topics in which all feel an interest, and which will not lead directly and pointedly to the subjects of disagreement.—
—Our ministers should seek to come near to the ministers of other denominations. Pray for and with these men, for whom Christ is interceding. A solemn responsibility is theirs. As Christ’s messengers, we should manifest a deep, earnest interest in these shepherds of the flock.— .
Courtesy of the Ellen G. White Estate, Inc.