Is there a term for defensive effects that only/primarily function for attacking creatures?
There isn't really an overarching term for these effects (official or unofficial, that I've heard anyway), as they're so broad. For many of them, it's simply abilities that trigger off of attacking

Winds of Qal Sima, Iroas and Dolmen Gate have one-sided fogs. Also in this category would be Endure and (depending on deck construction) Moonmist. This is less of a category and more of a sub-category of fog effects.

Legion Loyalist has a word for its ability on the card itself: Battalion, which is a triggered ability that encourages attacking with multiple creatures. A little specific for widespread use though...

I've head Hordechief and Odric's abilities and their ilk described as Battle Tactics or simply Tactical, with Odric as its namesake, but again, this style of ability doesn't show up often enough to really warrant its own name.

Lastly, someone commented to add Gustcloak Savior and its ilk to the list. I've heard to this kind of ability as Gustcloaking, or Recon, the latter name coming from the similar (but not identical) ability on the enchantment Reconnaissance.