The fanboys will get over it soon, and then you can stop banning MF. Until then, she's still a really good adc. Ban her to not see her on your team or the enemies.
edit: We're banning MF because you don't want to see MF support... not because it's broken...
Why should you ban it? Harass supports has been viable option since season 1. Season 5 gave them huge advantage over healer support due buff on adcs. Most harassers does not get it relic shield is the way to go for ranged - it gives you decent heal and lots of gold.
My own opinion is simple: If you cannot play support yourself, do not give any demands to support when you play adc. You need support. You do not need kills really as every assist is gold too, and killed enemies give you more safe farm.
As a person who has probably played a majority of his games support I think MF support is only good in niche situations depending on the ADC left open. Regardless I do think Morg and Kayle might be good counters. Spell shield and zoning from Morg with decent to strong damage depending on build. Kayle has heals, slows, speed ups, ranged AOE poke, and great ult to help survive that combo.
