Wither with static effects ruling

I have a rules clarification question I couldn't find an answer to online :

I have Massacre Girl, Known Killer - she applied enough damage to an Ancient Copper Dragon over 2 turns for it to have -5/-5 counters on it (wither effect). Normally that would kill it, but my opponent's Ancient Copper Dragon has Sword of Hearth and Home equipped, giving it a static +2/+2.

Does wither overrule the static +2/+2 from the equipment, or is it holding on due to the +2/+2 regardless of the -5/-5 counters? Thanks!