Let's quickly define the term "connotation". A denotation is the actual dictionary or official definition of a word, but a connotation is the implied or cultural meaning that is associated with the word.
The answer to this question does depend, to some degree, on the context of the word "toads". Context is the setting of an event or thing, and the surroundings or context can lend background information necessary for truly interpreting or understanding something.
Regardless of this fact, "toads" tends to have a derogatory, or insulting, connotation. A toad is a "tailless amphibian with a short, stout body and short legs, typically having dry warty skin that can exude poison". Here, the comparison of a person to a toad could have multiple connotations: that person is non-human; that person is short, stout, squat; that person is warty and ugly; that person is poisonous.