Laura Ingraham is being boycotted because she decided to tweet a childish insult against one of the Parkland shooting victims. You realize that dozens of prominent media personalities have pushed back against the Parkland survivors, right? Why haven't they been boycotted too if boycotting was as simple and easy as you suggest?
I'm arguing against your position because it seems to lack knowledge of how complicated real world discourse is. The First Amendment bars the government from banning speech; this gives citizens the responsibility to police themselves and corporations. But you're arguing for that to be taken away so that there is basically citizens have no legal recourse against speech they dislike? So how are any boycotts justifiable?
If you were more aware of how things actually worked, you would easily be able to cite boycotts that have gone against left-leaning people. I'll help you: Remember Kathy Griffin? [0]
[0] http://www.sandiegouniontribune.com/opinion/the-conversation...
Numerous left-leaning celebrities, as well as personalities on CNN, have ripped into Trump. If what you fear was actually the reality, you would have no problem citing successful boycotts against left-leaning celebrities.
Dude, be honest. You are only OK with targeting advertisers because it lines up with your beliefs instead of allowing all speech and just making better arguments against those who you disagree.
Oh, surely this could never turn around on you!