The first scene of this play makes it clear that Alceste despises social conventions because he feels that they cause men to be untruthful to each other and lack integrity. The conversation between Alceste and Philinte makes clear that Alceste feels there should be no flattery in society, and he takes umbrage against his friend precisely because he has just witnessed him "feigning friendship" towards somebody he hardly knows. He expresses his view about "simulated friendship" in the following quote:
I want us to be men and say what we really mean in all circumstances. Let what we have in our hearts be apparent in our words; let it be our hearts that speak, and let us not allow our feelings to be concealed under a mask of empty compliments.
The motivation for Alceste's hatred of social niceties therefore stems from the way that he sees giving in to such social norms as being untruthful and dishonest. He clearly has a much more radical understanding of truth and integrity than others in this play, and this unyielding and extreme view causes him to hate social conventions and despise those who practise them.