Why was there tension between Catholics and Protestants in the Elizabethan times?

Shakespeare sneakily employs religious references and symbolism that his audiences would have been aware of to talk about the way the Queen oversaw the nation's religious affairs. When Elizabeth was made Queen of England after the death of Mary Tudor, her people had good reason to be concerned. Within more or less the past decade the nation had gone from Protestant under Edward VI to Catholic under Mary and now back to Protestant (jeeeez make your mind up). Neither Elizabeth nor her government was very enthusiastic at first about religious reform, knowing the problems that would ensure. At first, she simply banned preaching altogether to try and keep the peace, desperately afraid of Catholic revolt. Most Catholics were equally optimistic, assuming that a Catholic husband was all Elizabeth needed. It was the Protestant population, in fact, who wanted revenge for their fellow Englishmen who were exiled, imprisoned and burnt at the stake under Queen Mary.