A Canadian coming into Canada does not need to provide any extraneous information to CBSA. "I'm a Canadian entering Canada" is sufficient. The reason for you entering Canada is none of their business and you can tell them so, without fear of any consequences. Questioning your reasons is well outside their mandate/authority.

I was once asked by the immigration officer of my country "tell me why you are coming here and you long you plan to stay for" I asked him whether he had satisfactorily established my citizenship, and he said he had. I told him that his earlier question was an inappropriate abuse of his position and well outside his mandate. He stared at me for about five seconds and gave me back my passport, saying, "well, I cannot deny you entry into your own country, have a nice day." It was all very polite, but I did want to make a point that day.