As @thomas-lotze has mentioned, currently pip tooling does not do that as there is no corresponding --user option. But what I find is that I can check in ~/.local/bin and look for the specific pip#.# which looks to me like it corresponds to the --user option.
In my case:
antho@noctil: ~/.l/bin$ pwd
/home/antho/.local/bin
antho@noctil: ~/.l/bin$ ls pip*
pip pip2 pip2.7 pip3 pip3.5
And then just uninstall with the specific pip version.