It could be an oxymoron. 쳐드시다 is commonly used for swearing at elder person than the speaker. The speaker probably wanted to say 쳐먹다. But, he thought that it seemed very rude. So, he used the compromise 쳐드시다 by using 드시다 as an honorific expression of 먹다. Similarly, 당신 is commonly used for swearing at elder person.

I'd say it is a sarcasm. 처드시다 (not 쳐) is not something you would say in a normal situation. Either it is a sarcasm or maybe toning down the word a bit because 처먹다 might sound too strong for the occasion. 셨 and 심심하셨 in the same sentence are definitely sarcasm. The 처- prefix is quite offensive, tantamount to "screw you", so once it's said you're openly being nasty. Polite words mixed in are likely to be for a sarcastic effect, usually to gall the person even more by twisting things (but close friends might talk like this as a joke too, so it depends).