Yes. 10’s of thousands.
The Anabaptists pretty much had a “our way or the highway” attitude towards any residents of the city who didn’t get in line with their program. The lunacy continued for quite a few months while they were effectively cut off from the outside, and people started starving as well.
When the final siege started, the Anabaptists said that anyone who wanted to flee the city could, and hundreds of people took the chance to flee the impending sack of the city. Only problem was, when the ran into the Catholic lines, they were all slaughtered.
All this because some people didn’t believe in God the same way as they did?
I’d like to see the evidence for tens of thousands dead. Not those starved, but killed by policy. They only had a few months before they were surrounded, and none of the accounts I’ve found say anything about them killing people by the thousands, let alone by the tens of thousands.
Nor were their enemies exactly models of restraint and Christian charity:
“The army of Münster was defeated in 1536 by the prince bishop Franz von Waldeck, and John of Leiden was captured. He was found in the cellar of a house, from where he was taken to a dungeon in Dülmen, then brought back to Münster. On January 22, 1536, along with Bernhard Krechting and Bernhard Knipperdolling, he was tortured and then executed. Each of the three was attached to a pole by an iron spiked collar and his body ripped with red-hot tongs for the space of an hour. After Knipperdolling saw the process of torturing John of Leiden, he attempted to kill himself with the collar, using it to choke himself. After that the executioner tied him to the stake to make it impossible for him to kill himself. After the burning, their tongues were pulled out with tongs before each was killed with a burning dagger thrust through the heart. The bodies were placed in three cages and hung from the steeple of St. Lambert’s Church and the remains left to rot. About fifty years later the bones were removed, but the cages have remained into the 21st century.”
https://en.wikipedia.org/wiki/John_of_Leiden
I’ve been looking, and I can find no verification that the Anabaptist extremists killed thousands or tens of thousands.