I really don't see your problem, Jesus clearly spoke the Parable.
Jesus clearly spoke the Parable to the Pharisees, after finishing the Parable Jesus saked the the question.
Mat. 21:40
When the lord therefore of the vineyard cometh, what will he do unto those husbandmen?
The Pharisees answered Jesus this way,
Mat. 21:41
They say unto him, He will miserably destroy those wicked men, and will let out his vineyard unto other husbandmen, which shall render him the fruits in their seasons.
Jesus did not correct their answer to His question, He continued with what He was saying.
Mat 21:42 Jesus saith unto them, Did ye never read in the scriptures, The stone which the builders rejected, the same is become the head of the corner: this is the Lord's doing, and it is marvellous in our eyes?
Mat 21:43 Therefore say I unto you, The kingdom of God shall be taken from you, and given to a nation bringing forth the fruits thereof.
Mat 21:44 And whosoever shall fall on this stone shall be broken: but on whomsoever it shall fall, it will grind him to powder.
What Jesus has related to the Pharisees in these last three verses is essentially what their answer was,
"THEY as Wicked Men would be Destroyed Miserably."
In other words, The stone which the builders rejected, on whomsoever it shall fall, it will grind him to powder.......Destroyed Miserably.
Therefore say I unto you, The kingdom of God shall be taken from you, and given to a nation bringing forth the fruits thereof.
So, to answer your question as clearly as I can, Jesus asked the Pharisees a question at the end of His Parable, they in turn answered His question with the words.
They said unto him, "He will miserably destroy those wicked men"
Therefore it was them who said the words.
But we see in the Luke rendition of the Parable, Jesus spoke the words.
Does this essentially change the message given in either rendition, (NO).
Do each of these renditions contradict each other, (NO)
Look at it this way, there is a car accident, there are four eyewitnesses to the accident, each one will give a different account of what happened, but the essential elements of the truth will all be the same.
Lastly, remember, the account of this incident recorded by Luke was from eyewitnesses that he himself interviewed because, he was not an eyewitness himself, he therefore had a mix of recollections form more than one eyewitness.
Sorry for the length of this post but I was trying to cover every base I could think of.