I've dealt with this subject before in a previous post. Basically, drowning an animal is not kind. The animal suffers. Putting it in a sack and thumping it over the head with a weighty object may sound callous, even cruel (depending on how you define 'cruel', but that's a post for another day). But it's humane - the animal doesn't see it coming, loses consciousness instantly, and promptly dies without regaining consciousness. Job done, minimum suffering.
But the RSPCA don't want you to know that. They just want you running scared. Don't be intimidated. Read up on what the RSPCA are really about (63,321 animals killed in 2009) - and keep killing those squirrels.
Coincidentally (really?) the RSPB have a perfectly timed press release out, suggesting you use vaseline and chilli to keep the squirrels off your bird feeders. Funny, they're usually rather harsher than that on invasive alien species. Except the cute ones that visit their members' gardens I suppose.
Still, if you have the sort of neighbour that calls the RSPCA because you're culling pests, you can probably think of a use for all that vaseline and chilli.
UPDATE: Read Quentin Letts' opinion here » Preview:
Forty years ago, the Royal Society for the Prevention of Cruelty to Animals was a much-needed voice of mercy on animal matters... Today, sadly, it seems to be losing touch with common sense and is pursuing animal rights with a furious logic that seems to have more to do with vexatious litigiousness and a big-sister view of social engineering rather than balanced, public interest charity work.James Delingpole's not happy either...
AND THERE'S MORE: I read on the perennially entertaining Al Jahom that Tom Blades at BASC has suggested that people who catch a squirrel should pop it round to the RSPCA for them to dispose of. Genius! Since the sanctimonious buggers think that only they know the proper way to deal with the fluffy little vermin, let's land them with the problem - and the vets' bills. In fact, I think I'll go and drop a couple through the letterbox now, ready for when they open up tomorrow morning.