The composter provides a suitable habitat for the slugs, cool, dark,moist & plenty of food around.

And they do turn the stuff you put in the bin into compost.

No, leave 'em alone - the type of slug you have may be the ones that exist purely on dead vegetative material - see the link below, there's a section in it that talks about slugs in compost bins

https://www.gardenorganic.org.uk/composting-myths-exposed

They're helping to form the compost, but I would rather have earthworms in my compost than slugs! The best thing that I can think of is to pick them out (with gloves) and feed the birds when you turn the compost.

Tug must have better birds than we have here. Even our hens would not eat slugs unless they were squashed for them.
Removing the slugs would be a waste of time as any not eaten would very quickly (for a slug) move back in.

Well, I remember reading a discussion on GoY about the various birds that would eat slugs in the UK. If those birds aren't in your neighborhood, then bag 'em and bin 'em, I guess. Others will hatch, and others will move in, but each round of removals should be smaller. The ultimate goal is to have fewer eggs and babies in the compost when you spread it on the garden.

My pet turtle loves slugs. He's a red ear slider.

When I find slugs in my garden I always give them a chance and put them in a compost bin. I think they might survive in that mass of vegeatation and contribute to my compost.

Mine doesn't seem bad in the daytime but at night its just heaving with them. If they can process the compost instead of my plants I don't mind - they seem to have gone when the compost is ready for use. (Though best keep a look out for eggs...)

Those big black (and brown) ones are actually cannibals. They eat other slugs so they are doing you a favour by reducing the population of the small er slugs which eat plant material.