आत्मा + उपम्य​ = आत्मौपम्य​ ; उपम्य​ means 'Having compared" ; आत्मा could mean "oneself" or "soul".. Since the context is comparison, I would interpret आत्मा as "oneself". since आत्मा is in
प्रथमा विभक्तिः (nominative case), it is subject.. The verb form उपम्य​ is an action performed by subject आत्मा. The object is missing here, or its implicit. I would interpret the object as आत्मानम् (oneself as in accusative case). So "oneself is comparing himself to _______" We can interpret the missing word as इतरैः (with others). So my interpretation would be आत्मा आत्मानं इतरैः उपम्य where the second and third words are implicit. I don't think it would be in a negative sense. It should mean "view others as you view yourself".