Our brothers, sisters, mothers and fathers who are gay have been discriminated against, harassed, oppressed, put down, beaten up, ostracized, put in jail, placed in psych wards, put on medication, murdered by their neighbors, family, communities, gov't - local, state and federal. They've been forced to hide, lie about their lives for eons - Only in the last few decades have they been slowly accepted into their communities across this nation. Their parade may seem like flaunting and forcing this issue and it is to a degree, but what it also does is send a message to those who have been disenfranchised and who are unsure and still afraid (because they are being humiliated in their own communities) to come out to live their lives fully without fear, there are places they can be where they are fully accepted and have nothing to fear. If they want to have a parade, so be it.
And if you've actually seen one of their parades you wouldn't be so negative.
As for the Straight parade - Straight people are not being discriminated against, harassed, oppressed, put down, beaten up.... because of their sexuality. They think it's clever but It's a bullshit parade of fearmongering and hate.
So yeah, big difference.