I'm sorry, but I think that you're misunderstanding the goals of the bus. It attemps to concientize about how too liberal governments (specially on Spain and Germany) are trying to force sex-education programs in children too young to understand them. The fact that those new programs are LGBT-focused add to the issue, since parents see that as an attack against their children.
HazteOir has been with their bus for a long while, not only on Spain, but on New York, South America, Mexico and recently, Germany. Mexico conservative majority welcomed the bus as soon as it arrived (HazteOir is partially financed by the mexican association El Yunque). That aside, I haven't known of any member of the LGBT community that has been harmed for the bus activities, while on the other hand, many buses have been attacked or vandalized.
This is a delicate issue, but in the end, I think that those parents and other people deserve the same amount of free speech than the LGBT lobby, as long as none of the parties harm the other group. And actually, I kinda support the bus message, since teaching sex-related things to children so young feels...wrong. Quite ironic since, as a homosexual man, I should support the LGBT groups, but sadly, after all that I've seen, that's not the case.
Luckily for us, the world seems a much safer place for homosexual people than in the XIX century, but instead of forcing pro-LGBT laws on heterosexual people, like some radical-liberal parties are proposing, the goals of the community should be seeking for the safety of homosexual minorities that are actually being prosecuted or outright murdered, like those on the Middle East, southern Asia and Central Africa. Harassing the conservative-heterosexual side of our relatively-civilized society is only going to backfire, and doing that while ignoring the pleas of the people the really need this support it's a bit hypocritical.
That was too long of a rant, but in the end, I think that we shouldn't label anyone as a bigot only because they haven't a liberal mindset. As long as they're not hostile, each side ideas are equally valuable.