Perhaps Google thinks its market position is so strong that it doesn’t have to worry about piddly things like whether its employees spend a great deal of time using internal systems to slander half the company’s American customer base. What are you going to do, use another search engine?
But this is too narrow an analysis. For one thing, there are quite a lot of conservative small-business owners, and small business is the lifeblood of the kinds of ads that Google sells. The company will be hurt if those business owners get serious about taking their advertising elsewhere, especially if conservatives pursue a secondary boycott, targeting companies that advertise with Google.
To be sure, boycotts are rarely all that effective. But most boycotts involve minor matters of policy. This is about tribal identity. Google fired a conservative for writing a rather anodyne memo. If it turns out that the company was at the same time tolerating truly vicious conservative bashing in its internal systems—well, no one wants to give their hard-earned money to people or companies that are violently bigoted against them.