Walter Martin is a wacko, and I'm no JW. He claims to have had an advanced degree he didn't have and he didn't really show an understanding of the scriptures. He always reminded me of the kind of guy who would slip a gold cap onto a tooth before going out and giving a sermon. As someone who's studied the gun control issue for years, I found the same sort of intellectual dishonesty with John Lott (though I'm on the same side politically). Once someone does something dishonest, I'm not quick to believe them. (Lott would write articles for publication, then write "letters" praising himself under psuedonyms. Do a Google search.)
While the Jehovah's Witnesses are wrong, in my view, that's a long way from saying they're damned to hell or are a "cult." Those who claim to know that people are damned for their beliefs should be more concerned with their own souls. It nowhere says in the scriptures that anyone will be damned for their sincere beliefs. It's neither just or merciful, two of the crowning attributes of God. People who presume to speak for God are prophets, either true or false. I'll let you all decide which Walter Martin falls into. Christ's message was one of love and understanding. Martin pretended to "love" those whom he condemned, but it was love based in warning.
As much as I don't agree with the Witnesses, I warn people who want to rip their friends and family from the religion without having something to replace it with. People who have their belief systems torn away from them can lose their entire reason for living. They've even been known to commit suicide and divorce those who did the tearing. When Jesus said he would be a devisive person, he meant it for those who accepted him being opposed by those who didn't. He didn't mean to destroy the faith of others for "Him," or for "love" or any other ultimately self-centered reason.
Since Martin is dead, I'm sure he's probably already taken the issue up with those on the other side. I've never held much respect for those who think everyone else but them are damned. One noted minister was heard years ago arguing pointedly about something with his wife. When they got to the checkout line, the wife stormed off down an aisle, turned around and said, "If you're correct, dear, there's only going to be two people in Heaven -- you and God!
P.S. -- I know there are such things as dangerous cults, and when a religion forces a person from having contact with their family and depriving them of food and sleep, or making them eat bad food, that's something completely different. Jehovah's Witnesses, Mormons, Seventh Day Adventists, and Worldwide Church of God are not cults any more than early Christianity was a cult.