George I's hatred of the Tories was the product of the king's – in some cases fully justified – suspicion that many of them were Jacobites who would prefer to see the Stuart dynasty restored.
1715 was a difficult year for the new Hanoverian dynasty - it was the year of the first Jacobite uprising in Scotland – but it was also the culmination of a whole period of uncertainty and disorder which dated back to the last years of Queen Anne. Many of these problems grew out of riots rooted in holiday gatherings and public celebrations that were, in this period, frequently organised and sponsored by political factions (the Whigs were actually the first group to seek to harness the power of the mob, organising "pope-burning" ceremonies in the late 17th century, the descendants of which can still be seen in the Bonfire Night celebrations in Lewes.) The Sacheverell Riots of 1710, which saw Tory supporters attack nonconformists across much of England, including London, were followed up by further rioting associated with (and protesting) George's coronation in 1714, eventually leading to the passage of the well-known Riot Act in 1715, which gave the government new and sweeping powers to deal with such disorder.
It was fear that these riots might only be the start of more serious disorder that prompted George I to turn to the – then stridently anti-Catholic – Whigs for political support. Thus the Duke of Newcastle reported in July 1721, when rumours of a Tory return to power were circulating, that
"the report of the Tories coming in having reached the King's ears, he has been so good as to declare to me and many other of his servants the concern that he has at the report, and has assured us that he neither has or ever had any such thoughts, and is determined to stand by the Whigs, and not take any one single Tory. He is very sensible the Whig party is the only security he has to depend on, in which he is most certainly right."
Sources
Ragnhild Hatton, George I (2001)
Geoffrey Holmes, "The Sacheverell Riots: The Crowd and the Church in Early Eighteenth-Century London" Past & Present 72 (1976)
Robert Brink Shoemaker, The London Mob: Violence and Disorder in Eighteenth-century England (2004)