As other have pointed out above, the point is not where you think it is coming from, it is where it is actually coming from. Someone could easily man in the middle the connection and change the code you download, so your computer ran whatever they wanted you to run.
You say someone could "easily" man-in-the-middle the connection, but is it really that easy? Or likely? (Assuming you're not installing it from a random public wifi hotspot.)
Even so, assuming you want to be extra careful (you're installing it on a development machine with highly sensitive information), it's not that difficult to clone the repo and edit the install script to install from your local copy of the repo.
Comments
As other have pointed out above, the point is not where you think it is coming from, it is where it is actually coming from. Someone could easily man in the middle the connection and change the code you download, so your computer ran whatever they wanted you to run.
You say someone could "easily" man-in-the-middle the connection, but is it really that easy? Or likely? (Assuming you're not installing it from a random public wifi hotspot.)
Even so, assuming you want to be extra careful (you're installing it on a development machine with highly sensitive information), it's not that difficult to clone the repo and edit the install script to install from your local copy of the repo.