Not to be a broken record, but I would argue the two-party system disincentivizes social justice as a political priority by decreasing the ability of voters to withhold their vote based on lack of sufficient social justice consideration in a national presidential candidate's platform (because, hey, the other guy sucks in ALL respects, instead of just some), thus pushing politicians to focus on issues that affect the largest number of voters (i.e. economics, healthcare, infrastructure, the military, etc.).
In short, this is absolutely the smart move, electorally, whatever one thinks of it, morally.