Useless?

Xander might not have always been in a good relationship with his father, but he was sure his father had never mentioned those names the unknown man had just spewed. 

"I think you're talking to the wrong person," he said. 

Bruce's eyes widened in amusement. However, before Xander could leave, he quickly asked, "You're Xander Wallace right? The son of Thomas Wallace?"

Not only did the man recognize him, but he also knew his father. 

To improve the "show, don't tell" aspect of the sentence, we can convey Xander's disregard for the facts through his actions and attitude. Here's a revised version:

Xander dismissed the facts with a sharp wave of his hand, his eyes narrowing at the man across from him. The stranger's mild demeanor might have fooled someone else, but Xander wasn't about to be swayed by polite words or a harmless smile.