From an outsider's point of view, just reading your thread and knowing nothing about the situation other than what you've explained here, I can take a guess as to what is going on.
"I have made a point of handling him every day."
"He hisses when I walk in the room still."
"I have never given this reptile any reason to see me as a threat."
The reason it hisses whenever you walk into the room is because it knows that you are going to handle it, no matter what, for you handle it every day. That in itself is a reason for it to see you as a threat if it doesn't like being picked up.
There are two main schools of thought for calming monitors down. Some people think you should handle them every day, others think you should leave them alone and let them get used to you on their own terms. Each of these techniques will produce results, so it isn't a matter of right or wrong, but sometimes monitors are better suited for one technique rather than another. I think you have enough evidence that handling your monitor daily is not the way to go, so it's time to try something new.
Leave it alone for a while. Don't pick it up, but continue to do your normal things, like spot clean, change water etc. Offer it plenty of hide spots and don't ever disturb it when it is in one. It may take a long time, but eventually the monitor will realise that you entering the room doesn't mean it is going to get picked up. Eventually, and it may take a long long time, it may become curious and come to check you out. Then you can start to interact with it, first by letting it crawl onto your hand. Slowly but surely you'll gain its trust and eventually it may cope with you picking it up. This technique requires a lot of patience, especially as it currently sees you as the person that picks it up every day. It will take a while to forget that.
If it is a young animal, you may find that you don't need all that much patience, for they get bolder as they get older, anyway.
It's also possible that your monitor may not calm down at all and you have to understand that such is the lottery of monitor keeping. It doesn't make it any less of an interesting animal to keep.