Her father would have killed every one of those soldiers, and he would have killed their families as well. Dany executed two traitors who betrayed their sworn Liege Lord, and in return spared the lives of hundreds of men. When the actual Westerosi law on oath breaking is an automatic death sentence, she not only gave them an out, but even Tyrion suggested taking the Black and Randall spat that at their faces. How many men would have continued to refuse to kneel had Dany beheaded the Tarlys? One blast from Drogon (that put an end to affairs within seconds) had all the doubters falling on their knees. That execution was quicker than the one Jon gave the Night's Watchmen who betrayed him, and it is sure as shyt a better way to go than being eaten alive by hungry dogs, which is something that Jon almost assuredly knew was bound to happen when he left Ramsay for Sansa. Unless of course you believe that Jon thought Sansa was just going to have a chat with Ramsay and that was all. Do you think it was Sansa that had Ramsay locked up in the kernel? Do you think it happened without Jon knowing about it?
We also have Arya talking about executing people for questioning Jon lol. That's cute.