Are hard items heavier than 2 kg forbidden to be placed in carry-on luggage in flights within Mexico?

I have the following massager that I sometimes bring in my carry-on luggage:

Product dimensions: 4 x 5 x 5 inches. Weight: 4.2 Pounds.

Massagers are in the list of permitted items for the TSA (https://www.dhs.gov/learn-what-i-can-bring-plane), though as usual the final decision lies in the hand of the security agents.

As I was taking a flight within Mexico for Christmas, the TIJ departure airport security refused me to keep it in my carry-on luggage. The reason I was given was that I could use it to kill someone on my way to MEX since it was hard and heavy. I had to go back to the airline check-in desk to have it placed as a checked in luggage. It's the first time I had this issue with this massager, however this was also the first time I flew within Mexico. There was some language barrier between the security staff and myself, and the check-in desk was about to close, so I couldn't ask for more information.

Was that security staff overly paranoid or is it typical for hard items heavier than 2 kg to be forbidden to be placed in carry-on luggage in flights within Mexico?

My carry-on luggage weight was lower than what I was authorized (15kg), so this wasn't some overweight issue.