I take "manipulation" to be somewhat similar to "lying." The distinction is intent. So, you have at least three scenarios:
- 1) You earnestly express a belief, and it happens to have the desired outcome.
- 2) You express a belief primarily because you know what outcome it will create.
- 3) And the grey area: You honestly hold a belief, but you're also well informed about how that belief must be presented to modify your outcome.
Realistically, most of us live in that third option. The distinction between a job interview, and say, a dinner out with a friend, is that you're highly incentivized during a job interview to present yourself in the best light possible. Most of us are aware of how we'll come off when we make a statement, and there's always some incentive to come off in a better light. But, a job interview generally removes the possibility for blunt honesty. "Well, of course I'm excited to work here. If I don't express that excitement, you won't hire me!" Such a frank appraisal isn't really possible in a job interview. But in another (ie, a social) context, you could make a sarcastic quip, or even just an honest appraisal of the situation. "I'm excited to see you, but being in this crowded restaurant is giving me a bit of a panic attack." Maybe that's not the best social tact, but the option is much more available in a social context.
I'm meandering a bit here, but I hope my point comes through. When we're stuck in that grey area of option #3 in most situations in every day life, we can generally chose to go with honesty if we prefer. In a job interview, our success and survival depends on forcing us toward option #2.