The Jehovah's Witnesses are a dangerous, anti-Christian cult. They deny many of the essential truths of the Christian faith.
The Jehovah's Witnesses, in rejecting essential Christian doctrine, places itself squarely in the realm of heresy.
Just because they interpret the Bible differently (even wrongly) doesn't make them a dangerous cult. It can be argued that anyone who accepts the Bible as the literal word of God is just as delusional as JWs. So calling them wrong and your brand of religion right doesn't make them dangerous or you any better than them when it comes to beliefs.
What makes a group, religious or otherwise, a dangerous cult is how it manipulates its members to the point of being harmful or deadly to its members.
We'll never all agree on whether JWs are dangerous or not. The blood doctrine has caused harm and death, so it can be argued that it is dangerous. They are coerced and indoctrinated to treat people who leave as evil and to shun family, which causes harm. But they don't require followers to turn over all money or property or to live on compounds or give up marriage mates or children.
Compared to The People's Temple, The Branch Davidians, Heaven's Gate and others like them, then no, JWs are not a dangerous cult, or at least a suicide cult. But from the perspective of being a free minded individual who wants the right to believe and act as they choose, then the JW religion is harmful, possibly dangerous, as it tears families apart and causes mental anquish.
The real problem with debating this is that it's best done with people who have escaped. Trying to reason with a current JW that he's in a "dangerous cult" is only going to drive him deeper into "mother's arms" for protection. Cult members never believe they're in a cult...until they escape. Even then it takes time to admit to themselves.