You'll have to talk to a Mac expert. Almost all Macs are configured with case insensitive file system, but advanced users can configure their Macs to have a case sensitive file system. There are many programs, not just Tableau, that don't run with a case sensitive file system.
If someone else set up your Mac for you, talk to them.
Sorry I can't be more helpful.
Was able to get this worked out with the help of the post above. Details are sparse, but here's what I did.
1) Create a new Volume in Disk Utility (I named mine Tableau). Make sure it's not encrypted.
2) Ensure the new Volume is mounted. It should be mounted at /Volumes/<whatever you named the volume in step 1>.
3) Download the Tableau Desktop application and mount the DMG.
4) Install the application from Terminal using the following:
sudo installer -pkg /Volumes/Tableau\ Desktop/Tableau\ Desktop.pkg -target /Volumes/<whatever you named the volume in step1>
5) In Finder open /Volumes/<whatever you named the volume in step1>/Applications/Tableau Desktop...