Why aliens would only be a threat if they were dicks...

So with Hawkings releasing recently about why we shouldn't broadcast our presense, I felt the need the weigh in on this topic. You know, because a part of me thinks I know more about Stephen-the-man-Hawkings right?

Really the only reason aliens would be a threat is because they were dicks. BUT, this is actually pretty viable. Lets look at some of the reasons we've seen in the past as to why aliens have come to be a problem.

1) Colonization
Other than being jerks this is actually somewhat of a valid threat, which is why i'm touching on it first. An overful planet of oxygen breathing life forms then starts to spread out looking for habitable planets. This is definitely a possibility. But there are a LOT of holes in this idea.
a) The air we breathe consists of 0.03% Carbon Dioxide, 0.93% argon, 20.95% oxygen and 78.09% Nitrogen. Followed by trace amount of all other kinds of fun stuff. Too much oxygen would be lethal to humans as i'm sure it would be to aliens if there was too much or not enough. At different atmospheric pressures the percentages of there different airs we need change to allow them to absorb into our system. There's a LOT of factors that make the air we breathe specific to earth life.
b) Gravity is a bitch! So is air pressure. If any of these are off by even say... 50% higher? That's a HUGE different, and not difficult to have happen on a planetary level.
c) Pre-existing life could be lethal. If a planet is perfect for human life, what does that mean? It means there's already life on the planet. This isn't a "maybe" scenario either. Our planet filtered itself because of the life in it, plants slowly filtering the air, evolving it to evolve. What if one of the microbes on the planet we go to think certain parts of our brain taste like candy, or LOVE bonding to the cells of our lungs? yup, D...E...D... ded.

2) Gold!
Ok the most people probably dont get the reference because the movie was sooooooooooo bad. In Battlefield Earth the race of giant aliens (played by Scientologists) wants earth gold.
So imagine this scenario if you will. You're a gold farmer... you're positive there's 20 pounds of gold 100 feet deep, so you get your shovel out and start shoveling. At the 10 foot mark, you slam into a gold vein containing tens of thousands of pounds of gold... but nope, you completely ignore it because you want the 20 pounds of gold much further down. That giant vein of gold you first hit is known as the Kuiper Belt. It's a giant asteroid field orbiting the solar system slightly past Pluto. It's full, FULL of asteroids that have all the metals you can possibly imagine. There are also giant chunks of methane and ammonia which can be used as fuels, water for drinking etc etc. Also, to reach the Kuiper belt, you have to fly past the Oort cloud, which is, again, a MASSIVE space of asteroids. Now yes, the Oort cloud has never been directly observed, but mehh, lets pretend.

3) The hassle vs the technology.
There are only like... 3 ways an alien civilization could get here, and only one of those ways in which things would really be an issue.
a) FTL (faster than light travel)
b) spacial travel (worm holes, teleportation, etc)
c) Generation ships
FTL ships I dont think would be a bother. Oh there's a planet, oh there's life on it, the next habitable planet on sensors is 3 days that way... off we go.
Spacial travel same thing, they'd just warp to the next place on the map.
Generation ships might be anxious. But even then, a generation ship that makes it all the way here without killing one another, i would think, would be a tight knit community. This, to me, would be a situation of a group of people who have strong loving ties, some would want to stay (assuming our gravity, air pressure and composition, and microbes wouldn't be letal to them) some would ask for help and leave.

In the end, I could easily see civilizations living in places like the kuiper belt. Effectively umlimited resources, you could spread out as far as you wanted. The technology that a civilization would attain by this time I would think would allow for super fast terraforming so like... Come here, terraform Mars, and we have buddies we can borrow sugar from.

Like I said, the only people that would have any reason to be a threat would be a civilization full of dicks. This being said though, a civiliation that does have the technology to make it all the way here wouldn't be defeated by a high pitched country folk song, or water, or anything really. We would just either wake up one day and they'd have won, or we wouldn't wake up.

So to Hawkings, I do agree. The risk of total anhilation, although seemingly low, isn't worth that risk. It's a shame though, first contact with a species of good willed people who just want to know they're not alone in the universe, would be spectacular.