It is, indeed, wrong. If you took your car to a mechanic and he told you that you needed a $500 repair job, but he was lying through his teeth, would you suddenly feel it was OK if he said, "But it was basically the only way I could get paid?" If you paid an investment broker for advice and he gave you false information but justified it as "but that's the only way I could get you to invest," would you feel it was OK? This is all hyperbolic, sure... but if you cheated on your taxes in order to get a tax refund, and your excuse was, "But that's the only way I could get a refund," I doubt the IRS would suddenly forgive you.

The clients are paying e-Rewards for legitimate and hopefully accurate market research. e-Rewards is paying (in a sense) its members to answer surveys truthfully, so that their client gets what they paid for. By answering falsely to get credit for a survey for which you do not qualify, you are defrauding both e-Rewards and its client.