The following is a Bible based answer. This is what Jehovah's Witnesses Believe.
These words to still apply today in the sense that there are many who claim to be Christians who are not really living as Christians and are promoting beliefs that do not harmonize with true Christianity as taught in the Bible. The ones doing this are helping Satan to accomplish his will because someone looking to be a Christian could be mislead by them as to what it means to be a Christian or what the Bible teaches.
Here are some scriptures that help us to see that there are still many today like this:
Many will say to me in that day: 'Lord, Lord, did we not prophecy in
your name, and expel demons in your name, and perform many powerful
works in your name?' And then I will declare to them: 'I never knew you!
Get away from me, your workers of lawlessness!'
I am not going to get into the time period of when "that day" refers to, but clearly just because many today claim to serve "the Lord" does not automatically make it true. If they make a practice out of disregarding Christian laws and principals, then they are really workers of lawlessness.
2 Timothy 3:1, 5
But know this, that in the last days critical times hard to deal
with will be here...having an appearance of godliness but proving
false to its power; and from these turn away.
Many today have an appearance of godliness, even an appearance of being Christian, but show with their life that God's standards have virtually no effect or power over them.
2 Timothy 4:3
For there will be a period of time when they will not put up with the
wholesome teaching, but according to their own desires, they will
surround themselves with teachers to have their ears tickled.
Many religious leaders today within Christendom will promote acceptance of things that flagrantly disregard Bible principals. Many will even publicly disavow large portions of the Bible as being accurate.
Exert yourselves vigorously to get in through the narrow door, because
many, I tell you, will seek to get in but will not be able.
Mathew 7:13, 14
"Go in through the narrow gate, because broad is the gate and spacious
the road leading off into destruction, and many are going in through
it; whereas narrow is the gate and cramped the road leading off into
life, and few are finding it.
Of the billions of people who think of themselves as "Christian" would it be reasonable to think that all of them are helping others to go down the cramped road leading to life? Doesn't it seem more reasonable that some of them are encouraging people to go down the broad and spacious road that is leading off into destruction?
one Lord, one faith, one baptism;
According to this scripture, Christians are supposed to be united. Can the collection of all Christian denominations be thought of as a collective, united group if they have distinctly contradictory beliefs? Wouldn't it be more in harmony with this scripture to believe that God is organized enough to use just one religious group to teach and help people to serve him unitedly and acceptably?
God is a Spirit, and those worshipping him must worship with spirit
This scripture helps us to see that in order for our worship to be acceptable to God, we must worship him in accordance with the truth. Could all religious leaders within all denominations be promoting the truth about how to worship God even though they teach contradictory ideas? Clearly that cannot be the case. Since God requires us to worship him with truth, then anyone promoting things not true is promoting worship that is not acceptable to God and is therefore a minister of Satan in the sense that they are serving his interests.
Of course there are sincere people within all religions and not all who are aiding Satan realize they are doing this. That is why we continue to preach to all that will listen. For more information, please see "How Can You Recognize True Worship?" in the brochure "Good News From God!".