You can still debate, protest, and make noise leading up to elections in order to influence people's vote. Once the election is over, however, you can't go on being a sore loser and openly work to undermine the country you live in. Boycotts are not an appropriate way of working for change in the framework of a Democratic society. If you don't like the way things are done, run for government.
Firebomb thrown during demonstration in northern Israeli town of Umm al Fahm (Haaretz)
from the article: The boycott law is unconstitutional and undemocratic