Maybe my basic position would be more clear if I put things this way:

1) We evolved a "sympathy module" in order to make it possible to operate in social groups effectively.

2) This module is fairly flexible. It isn't limited to just me and my offspring, for example.

3) This module is flexible enough to include any life form I can identify with.

4) How easily I can identify with life form X is directly related to how much sympathy I can feel for life form X.

5) In general, the ease with which we can identify with life form X is directly related with how similar they are to us. It's easiest, therefore, to identify with our close relatives, followed by other people, other primates, other mammels, etc. It's quite difficult to identify with an insect. It's next to impossible to identify with a leaf.

6) People tend to feel more sympathy for close relatives than strangers, other people than apes, apes than other mammels, other mammels than birds, birds than insects, and insects than leaves.