He likes to think his lies here have a good base, especially with how fast Knock Out was skidding around. Sure, maybe his already shitty morals are even more disconnected when dealing with Knock Out because ~ex-Decepticon~ but there are lines that even he wouldn't cross.

One of those being leaving Knock Out here to slowly bleed out, after he's seen Sentinel at the scene. Look, he'll even prove it; "Well, I'm not about to just sit here and watch you die, so. I can either carry you back orrrrr we'll have some new red spare parts."

He makes a 'weighing things' motion with his hands. What a hard choice this is.