Ok; here's my problem with calling them robots, mecha, gundams, etc.:
BattleTech is an American creation
inspired by Japanese mecha culture...but
distinctly Western in flavor. It tried to set itself apart from its origins by divorcing the term
mecha or
robot, and embracing these war machines as just that; Machines of War. Mechanical...but not
mecha. Mecha is a Japanese term for anything mechanical...BattleTech is...American.
In other words, these are massive walking tanks...huge mechanized armored combat vehicles piloted by highly trained soldiers. The term
robot, a Czech word incidentally, has different connotations. It suggest that these machines are autonomous entities, rather than vehicles. This is not the case.
So, while technically a BattleMech can be referred to as mecha or robot, a more accurate term is simply calling it a 'Mech...because that fits in better with the spirit of the BattleTech franchise.
That said, call these things whatever the hell you want.