(1) Laws are bad things. Most laws can at best be a necessary evil; they generally constrain the freedom of some people, to bring about what we see as a countervailing social good. If we forbid discrimination in employment for category X, that means we take away people's choice not to employ category X. Whether or not employers should discriminate against people in category X is irrelevant; it's not freedom if you can only do that of which society approves.
In addition, an anti discrimination law requires a staff to execute it, and results in businesses adopting practices to protect themselves against lawsuits. Both of these are counter-productive.
There are many things that are wrong, but should not be illegal. Lying, for example, is generally wrong, but should not be illegal except under very specific circumstances.
(2)If a law can at best be a necessary evil, this law fails the test of necessity. Omaha, the year after it passed its sexual orientation/gender discrimination ordinance, counted three actual cases of discrimination on the basis of sexual orientation/gender identity. There is simply no evidence gay or transgender people in Nebraska are suffering substantial unemployment because of discrimination. A feeling that you might once have been discriminated against is not a sufficient justification for this law.
Some of us, though libertarian, nonetheless support the 1964 Civil Rights Act, simply bacause discrimination at the time based on race and to a lesser extent based on sex was so pervasive that it constituted a genuine threat to the life and liberty of women and African-Americans. This is not the case at present with respect to sexual orientation or gender identity.
(3) While this bill covers only employment, as night follows day it will be followed by a law covering discrimination in public accomodations. Such laws have been used to force people to participate in activities that violate their conscience or desires. I don't believe in giving a special place to religious liberty (although the constitution does, and I think we should defer to the constitution), but if a photographer does not want to work a gay wedding, that should be his or her right. It's lousy business choice on his or her part, but maybe that's not important to him or her, and in any case it's none of our business.
(4) And finally, this bill is part of a general movement of intolerance of dissenting views in our society, particularly on the part of the 'gay-rights' movement. Brendan Eich was just hounded out of a CEO job at Mozilla for having six years ago contributed to Proposition 8, an anti-gay-marriage initiative in California. A similar hounding was attempted against Phil Robertson. Other proponents of Proposition 8 have been harassed. I don't agree with either of these gentlemen (especially Robertson) but I will defend to the death their right to hold, express, and act on their views. One should be generally skeptical of slippery slope arguments, but we know this slippery slope exists, and we've seen it in action. It's time some people learned tolerance is a two-way street. If for no other reason, we tolerate others so we will receive tolerance in return.