Assuming that union supporters are invited to these meetings, at the very beginning of the meeting, rise, identify yourselves as union supporters and, very respectfully, declare that this meeting is taking many of you away from important work. Don't get into a confrontation and don't leave the meeting!  

Try to turn the meeting into a more democratic forum. By doing this you should be able to expose the boss' hypocrisy. He has no interest in an honest, open and democratic discussion and exchange of ideas! 

Propose to the person running the meeting that instead of a controlled, mandatory meeting that he should agree to a series of regular, perhaps weekly forums. Employees would be free to attend, voluntarily to ask any questions of management or union representatives. The forums would be held on company property for the convenience of employees. 

If they agree then all employees will get the whole truth about the union organizing campaign. If they say NO ask why are they afraid of free, open discussion. Ask why we are all required to sit here and listen to just one side of the story? 

As a rule, it's not a good idea to disrupt the owner's presentation, after your proposals have been rejected. Remember, he is really speaking to the "swing" and "undecided" voters and he has been prepared to turn your interruptions or disrespect to his advantage in the eyes of the voters he is targeting. 

During the owner's presentation, try to respond to the things he says and try to set the record straight. Don't let the lies and distortions go unchallenged! But, do it respectfully!! 

If you are asked to leave, do so; but, first, try to shame them, in the eyes of your co-workers, for the undemocratic and disrespectful nature of the proceedings. 

If union supporters are not invited, you should nevertheless show up at the meeting and try to gain entrance. Your strongest argument is, once again, the one of democracy and respect. 

When the meeting is over, talk to every identified union supporter to determine what effect the boss' performance had on them!