The thicker the atmosphere, the more light gets reflected or radiated away from the surface. So yes, the max temperature should go down during the day. At night however, the thicker atmosphere is more of a trapping blanket and the min temp goes up. The average stays the same between day and night, but the max and min tighten in a thicker atmosphere. Venus is closer to sun with higher average temp. Mars is farther from sun with lower average temp. Temps with respect to Earth average. Now temps are just an activity measure. Basically the motion of molecules. Temperature does not tell you how many molecules are moving. To understand energy density requires real science and leftist are no where close to that level yet.
Molecules should read molecules and atoms.