This is a common problem for two main factors:
1) newcomers don't realize the POWER of diplomacy. Talking to neighbors early on is key to preventing this from happening.
2) New comers are often seen as an easy target. It starts as 1-2 people attacking you, but then others see it as an opportunity to grab an extra factory or generator.
Best thing you can do is tough it out, and not give up easily. It gets more difficult to eliminate a player as they centralize drills, specialists, and stack queen hires. You'll learn a lot from this experience.
Like the guys above I try to help newcomers out; a few bits of advice, a peaceful border and friendly chat go a long way.
"I work for the company. But don't let that fool you, I'm really an okay guy."