Micro level Heterosexism is an individual not accepting gay individuals in everyday practice. For example, not hanging out with a gay person based on there sexual orientation for that reason alone

Heterosexism is a system of attitudes, bias, and discrimination in favor of opposite-sex sexuality and relationships. It can include the presumption that other people are heterosexual or that opposite-sex attractions and relationships are the only norm and therefore superior.

Joan McArthur-Blair has written:

'Gender and diversity' -- subject(s): Sex discrimination against women, Heterosexism, Affirmative action programs, Discrimination in higher education, Prevention

Most people refer to that as homophobia, and the people who have it as homophobes. However, homophobia implies a fear of gays, as opposed to just a prejudice.

Heterosexism is increasingly being used because it implies prejudice instead of fear.

Serge Parravano has written the novel "Keeping At It" which follows the story of a young man struggling to keep his life together after a tragic event.