Would it make you feel better if you told your dog there was a pill in the peanut butter? I don't think that would stop them from eating it.

No, because I don't feel the deception is bad in this case. It is a good deception.

If I showed my dog the pill, and then showed my dog the peanut butter, and then showed my dog the act of me putting peanut butter on the pill before giving him this package, where does the deception lie in this sequence of events?

If the dog was familiar with pills and already had an aversion to them, which is typically the case when people resort to using peanut butter, it is possible the dog would be suspicious and just try to lick the peanut butter and avoid the pill itself. Or just avoid it altogether. Typically you would not show your dog the pill going in the peanut butter.

It would not be a deception in the scenario you presented, but it also might not be effective in getting the dog to swallow the pill.