hehehehe... sorry... but hey, those two Yeerks were the only exception. And the reason they loved was probably because their hosts also loved each other... thus influencing them. But... I really can't imagine Yeerks loving... sure, friendship and loyalty were existing.. .but not really love... except Visser One and his subordinate of course...
Visser One and Essam was a special case, I agree, as they were very much influenced by the emotions of their hosts. However, there are other examples of Yeerk love where the hosts don't come into it at all: Aftran's love for her brother, which prompted her to, dangerously, follow a suspected Andalite bandit, and to steal a Dracon Beam, the punishment for which is "very painful". And I think with Yeerks, "very painful" means PAINFUL.
There's also the example of Eslin, who betrayed V3 and worked with an Andalite (consider how much the two species hate each other), due to his love/friendship for Derane. He describes this as originating very early on and continuing throughout their respective rise through the ranks through numerous hosts. And the way he describes it seems pretty close to the way human love might be described.
Visser One and Essam (and their love for their human children) was really human love, and wouldn't have occured without the confusion between themselves and their hosts. It's actually a really bad example of Yeerk love. However, the other two examples clearly stem from the Yeerks themselves.
I know this is an old quote, but I felt the need to answer this.