Thompson graduated from Ionview Public School and Sir John A. Macdonald Collegiate in Scarborough. Prior to being elected as a city councillor, he worked in the financial services industry, and founded a business services company.
He entered local politics in 1994 but was defeated in his attempt to win election to Metro Toronto council by Norm Kelly. In 1998 he became assistant to Councillor Lorenzo Berardinetti. When Berardinetti was elected to the Legislative Assembly of Ontario, Thompson successfully ran to replace him in the 2003 Toronto municipal election.
With a focus on "law and order" issues, Thompson is considered one of the more right-wing members of Toronto council. Soon after his election, he earned considerable and generally positive media attention for his forceful calls to address urban violence. He campaigned for a time to retain Julian Fantino as chief of the Toronto Police Service, and also pushed for a hotline to report troublesome rodents.
In the summer of 2005, during what many saw as a wave of shootings in Toronto, particularly in certain low-income neighbourhoods, Thompson garnered national attention for a suggestion that Toronto police should potentially be allowed or expected to stop and search young Black Canadian males at random. Thompson argued that a large percentage of the guns being used and a large number of victims are in the black community. Many accused Thompson of racial profiling and also expressed surprise that a black politician would suggest such an idea. Thompson himself said that he did not actually suggest racial profiling and later clarified his proposal, stating that he would not call for police to pull people over just because they're black, but rather because gun violence was affecting the black community. Thompson said that phone calls and e-mails received by his office had been mostly positive.
Despite this, Thompson quickly withdrew the suggestion, saying it was "not an idea we can or should try", and characterizing his comment as an "off-the-cuff" remark born of frustration with recent violence. Some critics suggested it could have been a calculated attempt to position himself for political advantage, perhaps for a conservative candidacy for mayor. Thompson denied he was thinking of a mayoral run.
Thompson and other Scarborough-area city councillors are currently campaigning to replace the Scarborough RT with a tunnelled extension of the Bloor-Danforth subway, arguing they could gain more ridership than the proposed Spadina line extension to York University.
In November 2013, during the Rob Ford scandal over his behavior and drug use, city Councillors met to question Ford. Thompson questioned Ford about an alleged crack house. Ford replied “Have you visited the house? Have you walked in the house?” Thompson replied “I have no interest in being in that house. I am not a crack user.”
Thompson was re-elected in the 2014 municipal election with over 80% of the vote.
In May 2017, Thompson helped Air Canada crew and other passengers restrain an unruly passenger who allegedly tried to open a cabin door on a flight from Jamaica to Toronto, which had to subsequently be diverted to Orlando, Florida.
Unofficial results as of October 27, 2014 11:51 PM
2010 City Clerk's Official Declaration of Results
2006 City Clerk's Official Declaration of Results
2003 City Clerk's Official Declaration of Results