They do they just aren't as active in their opposition. Trying to bring down any industry as massive as those surrounding beef and poultry production would be a very uphill battle, so they try to strike blows for animal rights where they can. I would think that the main reason they are more active in their opposition against seal hunting is because the beef and poultry industries are seen by the majority of the populous as established and accepted social and economic conventions, it's difficult to make people think that something they've been doing for years is cruel or immoral, even when it is.
Whereas seal hunting is lesser known, not as universally established in the minds of most people as something that "Just happens", and therefor more likely to raise the moral uproar from the general populous that any successful animal rights movement usually has to capitalise on. More.
I cant really gove you an answer,but what I can give you is a way to a solution, that is you have to find the anglde that you relate to or peaks your interest. A good paper is one that people get drawn into because it reaches them ln some way.As for me WW11 to me, I think of the holocaust and the effect it had on the survivors, their families and those who stood by and did nothing until it was too late.