Was Harry Houdini, in his day, hated as much by spiritualists and mystical thinkers as The Amazing Randi is today?

I would say that is pretty close to the truth................

Yes and no. Harry Houdini was part of a movement to debunk spiritualism. He attended seances in disguise and denounced all the people he observed who claimed to be spirit mediums as frauds. This angered some people, such as the author best known for his Sherlock Holmes stories, Arthur Conan Doyle, who publicly espoused spiritualism.

One difference between these two magician-debunkers is that, whereas there is evidence that Houdini was religious, or at least not an atheist, James Randi is a crusader against all forms of supernatural belief and a dogmatic atheist.

The Wikipedia article about Houdini says that he belonged to a Masonic lodge. Belief in God is a requirement for membership in the Masons. The Wiki also relates a story indicating that Houdini at least believed in the possibility of afterlife. It says,

"Before Houdini died, he and his wife agreed that if Houdini found it possible to communicate after death, he would communicate the message "Rosabelle believe", a secret code which they agreed to use. Rosabelle was their favorite song. Bess held yearly séances on Halloween for ten years after Houdini's death. She did claim to have contact through Arthur Ford in 1929 when Ford conveyed the secret code, but Bess later said the incident had been faked. The code seems to have been such that it could be broken by Ford or his associates using existing clues."

Houdini never claimed to be anything but a stage magician. Randi opines about the near-death experience studies conducted by physicians, although his knowledge of medical science is limited to sawing attractive female assistants in half. In a word, Randi has figured out the universe.

The hubris of James Randi reminds us of the unforgettable performance and costume of Jack Palance in The Silver Chalice.

https://www.youtube.com/watch?v=8dHzAn1vhl0