Isn't it Republicans who think this way. What is the diversity do you see within both parties. Actually the case isn't if minorities inherently vote Dems, its how many minorities can gain position of power within the 2 groups. Does the GOP want a more diverse membership. Are they embracing, Blacks, Asians Hispanic etc. How would the party change if it becomes more diverse. Saying minorities are looking to be Republicans more than Dems might be a 2 edge sword. I hope you get what you are asking for.
Look at how more and more minorities, especially when they become more independent and less reliant on government vote Republican based on their ideas. A lot of Hispanics are starting to agree with Republicans that we need a stronger border because illegal immigrants are hurting their communities (gangs, stealing their jobs, drugs, etc).