Loving Krishna means loving everyone because Krsna is in their heart. Conversely, applying that logic backwards, if you don’t love everyone, it means that you are not loving Krsna. Using the root and leaves example, if the leaves are looking healthy, it is to be understood that the root is receiving nourishment.
In SB, eleventh canto, it is explained that only the kanishta or neophyte sees Krsna in the temple, but not in the hearts of all, and fails to respect and develop loving relationships with them. In my experience, the leaves and root example has been used in our preaching to discourage against trying to develop loving relationships that are devoid of a sense of everyone’s natural attachment to the tree of Krsna, who alone can fulfill of their insatiable need for happiness forever.
But there is an important consideration which needs to be taken into account. While it is true that while ignoring the root, the leaves will suffer, one must keep in mind also the limitation of the tree example. Unlike a tree, the root is within the heart of the very leaf itself. It is not that by offering respect to Krsna in the temple, at the same time ignoring His presence in the hearts of all living entities, somehow all living entities will be satisfied. Why? Because that is not bhakti. Lord Kapiladeva in 3rd Canto SB says that such attempted worship is like pouring ghee into ashes- utterly ineffective.
Pouring water on the root means to actually offer love, otherwise one is pouring something else. Only water will work, not oil, molten lead or some other liquid. These will cause the leaves to wither. Kanishta adhikari worship of the Deity in the temple, is like pouring molten lead on the root of the tree, or perhaps old cooking oil. It is old because it has been used to cook our material desires- for exploitation of other living entities for self-aggrandizement (material).
If we are pouring actual water, or giving our bhakti to Krsna, then simultaneously, and by the exact same increments, we should see our love for every one of his parts and parcels grow. Thus, one’s heart expands. It has to- Krsna is bigger than the biggest! The universes reside within His form. Loving Him means your heart explodes with love for the whole creation.
Thus a devotee develops friendly loving relationships with all living entities.