Of course it is a valid choice. The major highways such as I-96 run east-west, and the historical nature of the link sets precedent for it to be maintained. Partisanship is an obvious excuse as the seat has been held by a Democrat in recent years.
The point is that Livingston County has
far more in common with points east than with points west, north, or south. To create a Livingston-based district with the
best possible community of interest would require the district to pick up portions of Oakland County.
Ingham County also has
far more in common with the rest of its Metropolitan area (Eaton, Clinton Counties, possibly Shiawassee) than it does with Livingston County. To create a Lansing-based district with the
best possible community of interest would require Ingham, Eaton, and Clinton to be in the same district, and that Livingston County be excluded from that district.
For the billionth time, this is not a matter of partisanship. The discussion is on creating a map that
best preserves communities of interest. The only partisanship involved is when your side hails a blatant Republican gerrymander as God's gift to redistricting, and then denounces a map that preserves communities of interest as a Democratic gerrymander.