Humans routinely drive other species on Earth to extinction, our own cousins. We also damage our own planet's environment.
It may be logical for an ET to just destroy us the way you might destroy a harmful bacteria, which might otherwise spread unpredictably. It wouldn't be about wanting slaves or raw resources (although as someone said, Earth itself might be considered somewhat valuable).
True, but my argument is that their intentions fundamentally don't matter. The real costs of acting on ill-intentions through interstellar space would probably give any real life Klingons or Romulans pause.
Meanwhile we fly, sometimes even into space, drive, walk outside, stay inside, eat/drink things that we shouldn't (but enjoy), and a thousand other risks which are substantially more real on an everyday basis... and many of those risks also come with rewards that can make life much more full and rich.
I think making contact with aliens would most likely just 1) confirm we weren't alone or 2) might actually be of benefit as we exchange knowledge and ideas, and/or 3) tell us that evolution tends to creates fearful, xenophobic entities where it also develops intelligence... in that order and with no further consequence than the knowledge.