I like toast. does not fully capture the semantics of I don't not like toast. (Or perhaps more grammatically correct; I don't dislike toast.)

"dislike" is not quite the same as "not like". At least in my observation, "dislike" fits between "ambivalent" and "hate":

"love" --- "like" --- "ambivalent" --- "dislike" --- "hate"

(At least as applies to the degree of liking something.)

So, "not like" would be any of "ambivalent", "dislike" or "hate", while "dislike" is a specific (range of) degree of (not) liking.

I understand what you are trying to say, but this was not a good example.