ANSWER: It's unquestionable that God certainly loved Satan (past tense), for Christians have always held the idea that Satan was God's highest creation.
A Scripture that speaks about this intimate relationship (I make the case for why this may still be informative about Satan even if the immediate context is about a Babylonian king here) is this:
Ezek 28:12-14
You were the seal of perfection,
full of wisdom and perfect in beauty.
You were in Eden, the garden of God.
Every kind of precious stone covered you:
carnelian, topaz, and diamond,
beryl, onyx, and jasper,
sapphire, turquoise and emerald.
Your mountings and settings were crafted in gold;
they were prepared on the day you were created.
You were an anointed guardian cherub,
for I had appointed you.
You were on the holy mountain of God;
you walked among the fiery stones.
Clearly, deep love is implied in the honor and position given to this anointed Guardian Cherub. God is love (1 John 4:16), so how would he not love this creature?
But even after he rebelled against God, God must still have loved Satan, simply because God continued to grant his Enemy life and existence. He even allowed him to come into his presence and converse and challenge God. (Job 1:6). The freedom God has given him up to this day shows God loves even this enemy.
You may counter, that this implies that God is evil, for he loves a being of pure evil. But Satan is not pure evil. Satan has a will bent on evil and he is totally, morally corrupt. But the fact that Satan has a will, is good. And Satan has personality, and power and intelligence, all of which are good. What God loves in Satan is what still remains of God (which is good), despite the monstrosity of his evil deeds and his complete depravity.
However, since Satan's will is utterly and unalterably set against God - his very name means "Adversary" - he's a different kind of enemy than humans can ever be. We are to love all human enemies because God sees every person as redeemable. God can reclaim any person and He specifically uses love to do it (Romans 2:4); that's why we wants us to love our enemies. By love we are engaging in God's chosen battle strategy for all his lost human enemies (Matt 5:45) - the ones he died for, while they were still his enemies (Rom 5:10).
However, we get no sense from Scripture that the fallen angels or their Leader are redeemable, so their rebellion must be final. So with demons we would never seek to bless them (that's what love does) because blessing can never turn them. In fact, blessing them (in whatever way that's possible) may actually help them turn us away from God!
Therefore, neither we nor God are obligated to love Satan by the same principle of blessing by which we love human enemies.
