Yes, corporate personhood is healthy for democracy, because corporate personhood allows for the exercise of freedom of speech. It is also important that individuals and entities be able to sue other entites when they are grieved. To do so, the corporation must be considered a person. Corporate personhood allows many people to influence politics by exercising their collective freedoms of speech.
Corporations are not people, nor should they be recognized as such. People - private, individual citizens - have a wide variety of worries and cares, and can support any politician they want. Corporations have huge amounts of money to support politicians, but only have narrow interests, allowing them to easily influence politicians who may be laregly indifferent towards their cause.