Your 'Training' Captain is incorrect in this instance. No damage will result. Wx radar is designed to be used on the ground prior to take-off. It should not be referenced during the TO roll (otherwise damage may result to the antenne, radome, wings, gear etc as you crash of the side of the RWY..
).
As you get more exposure and experience in the industry you will be able to be more discerning regarding what you hear from some other pilots. My advise would be to get into the books and refer to the printed word and talk to the Chief Pilot. Increase your knowledge and develop an understanding of what you are doing. This will enable you to eventually make the transition from Co-Pilot to Captain as you gain more experience and understanding of SOPs and the equipment that you use.
Knowledge of SOPs is key to effective CRM, Note the
Standard means a written standard, not what is 'usual' or what everybody else does. A practice may be unusual and yet still SOP. Effective CRM has 2 components: Safety and Efficiency. To arrive that these 2 goals, it is a requirement that
you know your books. This ideal means that use must know when you can and can't use the wx radar and also extends into things like checklist use during non-normals. Another example: Think about your home port: what RWY/TWYs can you use/not use? if you cannot answer these simple operational questions, then you are a burden to your Captain and a CRM threat.
Lack of knowledge is a dangerous thing.
PS: Some modern radars do not even need to be switched ON for the PWS system to work. They use a "pop-up" system in a passive mode.