Well, yes. Isnt that what gets praised about pre 4e spellcasters? That you can use all these cool spells to do things they are not intended to?
I go back to my chair analogy: A chair's primary use is to sit in. Because I could pick one up and hit you with it doesn't make it a weapon by definition.
But on a more serious note, Levitate is a 100% defense against melee monsters and Fly is enhanced movement speed as well as entrance into the 3d environment.
Its 100% useless in a dungeon with 10 ft ceilings. That's why I hate to call it a defensive buff. Its useful only when the situation is right, but as I said above, just because I can use it as a form of defense doesn't make it a combat spell, merely a spell with uses in combat.
Buff spells are buff spells, if someone is going to insist that Astral Seal, Direct the Strike, Hypnotism or Flame Arrows are attacks that cause damage.... I can point out just how nail shaped a lot screws and rivets are.
Hey, I'm not the one calling sleep damage!
4e has a lot more spells that are "combat" spells. I won't disagree there. I also saw its possible to but a non-combat (or at least, nonlethal) wizard as well. Points to them.
My point is that people are defining terms in very broad nets. If Sleep is a damaging spell or fly a combat buff, then no spell (or few spells) actually qualify as non-combat, which makes the definition useless. If I'm playing the wizard and I say "I'm prepping lots of combat magic" you're probably going to assume I have spells like Magic Missile, Fireball, or Summon Monster; not Light, Fly, or Dispel Magic.
3e made that more clearly defined, but Light has been used for attacks.
The problem when you're not arguing specific editions: I can argue from a d20-era PoV, you can argue AD&D, and someone else can argue 4e and we can use semantic tricks (like how light once had a combat use) to prove the other wrong.