Glenn you need to stick to trolling and kind of stay away from debate because you only seem to excel in one.

Proven intent to perform an illegal action is, in general, as sinister as actually performing the action. I'm sure you can contrive a situation where intent is innocent but I'm going to share an analogous maxim concerning whether a sexual desire is something you should be ashamed of or not:
Fact: If you have to spend hours in photoshop creating porn for your fetish because none exists, you have something wrong with you.
The analogy suggests that the longer you have to think to come up with a counterpoint to the statement "Proven intent to commit a crime should be as punishable as committing the crime", the less likely your point is correct.

Now, I forsee the counterpoint being something along the lines of a slippery slope fallacy: "Oh, so I should go to jail for murder if I tell you I want to strangle you?" This is, in fact, not really a fallacy because I haven't defined the specific scope of the phrase "intent" in my argument.

Among rational individuals, certain threats carry no teeth. When I do something that causes someone trouble and they say they wish they could strangle me, most people are able to understand this is a usage of hyperbole to express the concept "I am very frustrated with you right now!". When I say "proven intent to commit a crime" I do not speak of this situation at all. I mean to imply a situation where the person has made preparations and taken actions indicative of a meaningful desire to follow through with a criminal act.

When police set up a sting operation to catch drug offenders, intent is proven. The suspect initiates the transaction and it is clarified that their intent is to exchange money for drugs. At this point, the suspect has the capability to say "Ha ha just kidding" and walk away, and the police have no right to arrest him. It is only after the suspect agrees he wishes to exhange money for drugs then produces money that he is placed under arrest. There is a miniscule chance that he was still playing around at this point, but most people would understand it's not a good idea to walk up to a known drug dealer, offer money for drugs, then produce said money and take it away at the last minute.

For another example let's consider a successful sting I saw on a special about contract killers. The man was a pharmacist and had contacted an undercover policeman expressing interest in the murder of his wife. At this point he was a suspect and the police had no charges they could bring against him. A meeting was arranged, and he showed up to discuss details of the hit and provide payment. At this point, the police had excellent grounds for reasonable suspicious but still had no charges they could bring against him. The men discussed the details, and it was agreed that the pharmacist would provide a large amount of prescription narcotics in return for the crime. Even at this point, the police had no grounds for charges and the man could have walked out of the room innocent (but still creepy). Finally, the man produced a small bottle of narcotics for the down payment and handed it to the undercover policeman. They shook hands and said their parting words, in which the policeman included his code word for "come make the arrest". The man was completely innocent until he actually provided payment for the crime, at which point there is no possible way to refute the claim that he provided payment for a contract on another's life.

In the end, I believe the problem is actually that you are confusing "intent to commit a crime" with "going well out of your way to perform all of the actions characteristic of committing a crime, including agreeing upon payment and providing said payment". I am too lazy to go edit my post to reflect this conclusion, but perhaps this will prove a good test of reading comprehension for several of AGN's more developmentally challenged readers.

I highly doubt they arrested him as he boarded the plane to leave for Miami. He wasn't arrested after he left the plane. He wasn't arrested as soon as he reached the appointed place. Here, the article is scant on details, but it is clear he discussed fully his intent to submerge the children until they lost consciousness. My belief is that after payment was agreed upon and money changed hands, he found his face pressed against the table and handcuffs on his hands.

You cannot convince me you believe anyone in their right mind would initiate a conversation for such a thing, then book a flight, then describe in great detail his intents and produce money all as an elaborate prank. Anyone who thinks that's a good idea needs to spend some time reevaluating their sense of humor anyway.

*edit* That aside I do agree he deserves a fair trial as much as anyone else; even in the presence of abundant evidence the trial should never be forgone.