Stock prices are also influenced by supply & demand. The situation you describe works for just one company paying no corporation tax, but if every company suddenly has no corporation tax, every company's profits increase, so relative demand should stay the same, leaving prices the same.
Stocks can pay dividends which are a direct result of their profits, and so the corporate tax rate effects the amount of actual money that gets paid out. Stocks that don't pay dividends are an interesting case, that is the investors allow the company to reinvest their earnings for growth with the expectation of future dividends.
