Was Joseph Smith a martyr? That's a very good question. If you speak to any faithful Mormon (or TBM as they are sometimes known) the answer will be: "Why, yes! Of course he was! He was martyred at Carthage Jail!"
A martyr is someone who is put to death for his faith. "Like a lamb to the slaughter" is one definition of the act of being a martyr. Or Martyrdom as it is also known.
Generally, a martyr just accepts their fate and dies for their religion. They do not fight back. Some of them even make jokes about their martyrdom, and or forgive those that are martyring them.
Did anything like that happen in the case of Joseph Smith? No. It did not. Because Joseph Smith fought back. He drew a pistol on the mob who were attacking him and his companions and either injured or killed some of them.
Now, that was his right. Every man and woman has a right to defend themselves against attack. Even if this necessitates killing the attacker in extreme cases. And, let's face it, being attacked by a mob baying for your life is an extreme case.
But for followers of the church Joseph Smith founded to claim that Joseph Smith was a martyr is just plain wrong. A victim of a murderous attack, yes, he was. But a martyr? No. To describe Joseph Smith as a martyr is stretching the definition of that word beyond breaking point.
Here is a link to some 'real' martyrs for comparison:-