Pondělí is singular, so why is it plural in the answer?
Pondělí is plural as well: http://prirucka.ujc.cas.cz/?slovo=pond%C4%9Bl%C3%AD
Why isn't the expression "I hate Mondays" allowed?
Also, the construction used -- mít rád -- is generally translated as "like," while "hate" has its own Czech word, "nenávidět".
I think it is too strong.
I think it's a bit too strong. (Also, I don't like Mondays either.)