If your behind the bb5s and asking for cv support that could be a reason, if he is already support bb5-6s on front line or scouting that could be a reason.
A cv player is not entitled to protect your ship, its up to them who they want to cover and who they don't. I would cover a bb5-6 over a bb4 unless that bb4 is a skilled driver and pwning the enemy.
However ''Your a bb4 you dont get fighter cover'' is uncalled for. I have turned down request for help when i was to busy to send it (like tied up south keep sight for my team in massive enemy fps and AA). I have never giving a childish reason like that though.
Just ignore the kiddy stuff and play the game. Heck I don't even read chat half the time during battle, lol heck i don't even read chat 90% seating in battle waiting to go(mostly switch to web).