Have to say I'm a bit ambivalent on the whole subject of shareholder activism. Surely the purpose of shareholder engagement is preventing management from destroying value - Robin Geffen rallying the troops against Prudential's AIA bid would be a good example - rather than promoting a particular ethical or environmental cause (which others may disagree with).
Not saying those causes shouldn't be promoted, just that company AGMs are the wrong forum.
So I'm in the 'fund managers should walk away' camp but for different reasons. I just don't see the logic in buying a company (and therefore lowering its cost of capital etc.) that does something you fundamentally disagree with.
But as for whether oil companies are ethical - without oil the cost of living would be much higher than it is, and the quality of life would (in aggregate) be lower. So on balance, given their contribution to the sum of human happiness, I'm forced to conclude that they are ethical - at least until the alternatives become viable. I realise how that sounds!
Interested to hear other perspectives though.