Philippians 1:15-17

15 Some, it is true, [actually] preach Christ (the Messiah) [for no better reason than] out of envy and rivalry (party spirit), but others are doing so out of a loyal spirit and goodwill.

16 The latter [proclaim Christ] out of love, because they recognize and know that I am [providentially] put here for the defense of the good news (the Gospel).

17 But the former preach Christ out of a party spirit, insincerely [out of no pure motive, but thinking to annoy me], supposing they are making my bondage more bitter and my chains more galling.

The Truth is that many preachers and religious leaders are false. 

Beware of false prophets, who come to you dressed as sheep, but inside they are devouring wolves. Matthew 7:15

BUT THE [Holy] Spirit distinctly and expressly declares that in latter times some will turn away from the faith, giving attention to deluding and seducing spirits and doctrines that demons teach, Through the hypocrisy and pretensions of liars whose consciences are seared (cauterized), Who forbid people to marry and [teach them] to abstain from [certain kinds of] foods which God created to be received with thanksgiving by those who believe and have [an increasingly clear] knowledge of the truth. For everything God has created is good, and nothing is to be thrown away or refused if it is received with thanksgiving. For it is hallowed and consecrated by the Word of God and by prayer. 1 Timothy 4:1-5

So how do we know who is truly called to preach the Truth and who is a false prophet? We will know them by the fruit that our Father uses them to produce. 

But the fruit of the [Holy] Spirit [the work which His presence within accomplishes] is love, joy (gladness), peace, patience (an even temper, forbearance), kindness, goodness (benevolence), faithfulness, Gentleness (meekness, humility), self-control (self-restraint, continence). Against such things there is no law [that can bring a charge]. Galatians 5:22-23

Fruit is not a huge church building or earthly wealth. Fruit is exactly what our Father tells us that it is. Fruit is love. Fruit is patience, even when being persecuted. Fruit is being gentle while we intercede for the forgiveness of those who do not know what the Truth is. Fruit is running off religious bullies from a notable sinner and then not condemning them for their actions. You want to know who is truly called, look at how our Father has them act and treat the especially wicked. If they treat them as Jesus did, then they are truly preachers of the Gospel. If they treat them with harsh criticism, threats of Hell, and anger, then they are not true preachers of the Gospel. It is just that simple!