Convincing but False
It would be nice to think that everybody who claims to speak for God is one of His messengers. But that is not true. There are true prophets and false prophets. They may look and sound the same but they are very different on the inside. False prophets may speak in a very convincing manner and many people may be persuaded to follow them; but that does not make them true or safe. In fact, they are very dangerous.
Jesus told his disciples to be on their guard, to watch out for false prophets. God's people are like sheep, Jesus is the Lamb of God and pastors are God's under-shepherds. But the false prophets are really wolves even though they are dressed up to appear like sheep or shepherds. Their motive is not to build God's kingdom, but their own. They like to get people under their control in order to feed their own hunger for power and money. They do not want to serve and liberate the sheep; instead, they want to dominate and trap them. As they do so, they deprive the sheep of a balanced spiritual diet, and lead them away from the real Jesus, leaving them exposed to evil.
So how can we recognise false prophets? Jesus said that what is inside every person will always come out in some way. People may practice exciting words and actions; but look out for their reactions to unexpected circumstances, their lifestyle which will always reflect what is in their heart. In the same way that a thorn bush cannot produce sweet grapes, an evil heart cannot naturally express joy and peace. If a tree is diseased, it cannot produce good fruit. Neither can a false prophet lead people into truth.
False prophets are everywhere. They are Satan's secret agents; but often they do not realise that they themselves have been trapped, and their fleshliness is being manipulated to claim spiritual power. Watch out for them. Expect them to be there, as the Apostle Paul identified in the Ephesian church (Acts 20:29-31). They may do a lot of damage if left unchecked. However successful they may appear to be, God knows them - and if they do not repent they face the fire of God's wrath. So do not be naïve, discern who has God's approval before you follow.