No, you never hear anyone complaining about the FBI monitoring radical communists and socialists. Now the FBI is being run by radical communists and socialists. And why don't you hear anyone complaining about monitoring communists and socialists? Because they are a threat to the freedom and security of every single American (including themselves).
Is it wrong to monitory radical communists and socialists? It depends on if their rights are being violated. If they are then the government is, once again, becoming what it seeks to destroy.
The moral of the story: NEVER EVER TRUST THE GOVERNMENT. The government must be kept small and powerless. George Washington compared the government to a fire, if left unattended it can burn the house down. It must always be kept small and powerless. But that isn't at all what our government is today.