First of all, you will do well to not listen to Jehovah Witnesses, both in person and on line when it comes to biblical truth. This group has a very well-earned reputation for distorting the Bible, proof-texting and, when that does not work, mistranslating the Bible, for example, in their New World Translation. My advice is to stay away from their unhelpful false theories so that you can save yourself a lot of wasted time. My experience is that Jehovah Witnesses are trained to argue. They tend to argue but not to discuss truth. Their “faith” is largely of the head, but not of the heart. They do not believe that Jesus is God. They do not believe that he is deity. They do not believe that the Holy Spirit is a person. They have many false doctrines and even heretical beliefs, so why would you want to listen to this group?
But…. You have asked, so I will respond. The web site you sent me to is typical of Jehovah Witness argumentation. First of all, they love to argue. Second of all, they have the frustrating tendency of using one passage as a proof-text. They find a single passage on a particular topic, ignore all others on that topic, interpret that single passage in a particular way, declare that theirs is the only “logical” interpretation, and only then find a way to ignore all other relevant passages. This is EXACTLY what is happening with their use of 1 Peter 3:18. This passage says that Jesus was put to death in the body but made alive in the Spirit. What does this passage mean? I am not sure. This is a relatively difficult passage to interpret, so we ought to begin with other passages, not this one, to determine what it means that Jesus was made alive in the Spirit. Does this mean he was made alive by the Holy Spirit? Does it mean that he had a physical body? Does it mean that he did not have a physical body? Let us be honest. This passage is not sufficient to establish the answer. We ought to begin with more plain passages. For example, in John 21:4-14 Jesus ate fish with the disciples. Clearly he had a physical body if he was eating fish. What exactly does this mean? To be honest, I am not absolutely sure. Does this mean that Jesus’ resurrected body can take on physical form or not, depending on the need? Possibly. Then there is John 20:24-27 in which Thomas put his finger into the side of Jesus’ body, touching his partially healed wound. Again, it is clear from this passage that, at least in some sense, Jesus had a physical body after his resurrection. What kind of body was Jesus’ resurrected body? What kind will we have? Paul asks this question in 1 Cor 15:35. “With what kind of body will they come?” Please read the rest of 1 Corinthians 15. You will learn that we will have a different kind of body. Our current bodies are mortal, but our future bodies will be immortal. Everything I see in this section tells me that we will have bodies that have some sort of physical nature. Exactly what is this nature? I do not know, and I prefer not to speculate.
So, what is the truth? I believe we should be wise about this and say that we do not know exactly what our resurrected bodies will be like. Neither do we know exactly what Jesus’ resurrected body is like. It seems that there is a physical nature to these bodies, but we do not know exactly what that nature. We will be eating and drinking in the New Heaven and Earth, according to Revelation 22:1-5. Might this be metaphorical? Maybe. I feel that we would do well to be cautious to make too strong a statement about this. I believe that the passages we have that shed light on this are not absolutely definite as to what Jesus’ resurrected body was like, but we do know that it showed itself in physical form. To deny absolutely that Jesus’ resurrected body had a physical nature–to say that it was only a spiritual body–is not justified by scripture. I find their supposedly logical argument to be very unpersuasive. We would do well to allow this teaching on the exact nature of ours or Jesus’ resurrected body to be a mystery.
Let us go back to 1 Pet 3:18. To the JWs this is a proof text that Jesus’ resurrection body is spirit only. I am sorry, but this is not what the passage says. In fact, exactly what it is saying is not clear. Did Jesus take on a spirit-body in order to preach to the “spirits in prison?” Maybe. It is possible, but I simply do not have enough information in this passage to settle the question. From the John passages I am certain that Jesus’ resurrection body has physical qualities, but the interpretation of the somewhat obscure passage in 1 Pet 3:18 is simply not clear.
The use of the JWs of Hebrews 9:11-12 is totally unjustified. It says that he entered the [heavenly] Most Holy Place once for all by his own blood. This passage says nothing about the kind of body Jesus has post-resurrection! Then, at the web site, the JWs proceed to act on the assumption that they are already right. In other words, the interpret Genesis 18:1-8 and other passages based on the presupposition that neither angels nor Jesus has anything like a physical body. They simply state that angels are spirit beings, and that Jesus is a spirit-being. They then use this conclusion to prove that Jesus is a spirit-being. Where in the Bible does it say that angels are spirit-beings? This is circular reasoning. We would do well to not speak where the Bible does not speak. Maybe angels are purely spirit-beings? Who knows, but unless the Bible tells us this, this is Jehovah Witness speculation. There are plenty of reasons to thing that angels have something like a physical body, but certainly not like those we have. Let us only speak where the Bible speaks on such things.
I am sorry to give you a somewhat vague answer, but I want to suggest you not use anything from the Jehovah Witnesses as the starting point for any biblical teaching. They are notorious for abusing scripture to suit their own purposes.