Conspiracy theories about the MLK assassination are very common. I know people who think the FBI did it. Frankly, if the FBI wanted MLK out of the way, they wouldn't have had to kill him; they could have just leaked information to the press about his adulterous affairs.
There's a couple points in the article that are somewhat weak, though:
1. Eyewitness accounts are notoriously unreliable, and it's not unusual for multiple people at the scene of a crime to have conflicting accounts. If the detectives dismissed these other eyewitness accounts that said they heard the gunshot from the bushes (which would be an easy mistake to make), it's probably because forensics showed the shooting did not happen at that location.
2. The fact that James Earl Ray managed to flee police by going to different countries is irrelevant. It's like a creationist trying to point out how
fascinating it is that the "random, chaotic universe" just so happened to create a universe with all the planets aligned, a universe capable of sustaining life, etc.
3. James Earl Ray
constantly came up with new conspiracy theories about the killing in prison, blaming someone named "Raoul," despite the fact that a polygraph test showed he knew he was MLK's killer. Later, he did identify an auto worker named Raul as the accomplice, but
he was cleared. No mention is made of this alternate killer's identity except in the article cited above, where he is identified (without explanation) as Jules Ricco Kimble. Furthermore, Ray himself claimed that part of his motive for pleading guilty
was to get into a comfier prison, and people around him denied there was any pressure put on him to confess. EDIT: And despite the fact that the author of the article claims to have FBI files, he cites conspiracy theorist books. Real good job vetting his resources there.
