Theoretically agents could do these things, but most don't. They want deals to close. Giving you reasons not to buy doesn't close deals. If it turns out you don't like the house they'll be happy to sell it for you later.
It probably varies by the agent, but I have had good experience with a real estate agent being on the buying side. His reasoning was that the seller's agent was on the clock to close the deal on that one property he got assigned, whereas the buyer's agent would make roughly same amount of money on any property I would end up purchasing, so he had no reason to pressure me into closing.
A good conman leaves you feeling that you weren't cheated.