Teachings on emptiness are right on the borderline. There are many instances of being cautioned not to teach emptiness to those unprepared, because a premature exposure (without the proper foundation) could turn potential students away from Dharma and consign them to many more lives in samsara before they have another opportunity.
Having said that, this passage is quite clear, doesn't say anything outrageous, and is easily verifiable if you take the time to meditate or think on it. Please read it carefully:
Look at these offering materials like that: [Here Rinpoche is talking about the outer offerings made to the deities in the Yamantaka practice, which include drinking water, water for washing, incense, perfume, food, etc.] they are all created, first by the collective mental activity of a number of people on their mental level, followed by their practical interpretation, followed by their projection and perception. Combined together, those collective conditions are able to produce this. That's what's really meant by: there is no inherent existence. If there were inherent existence, you wouldn't need all those conditions; things would be there already, existing inherently.(Italics added)
For example, look at this round bread. Someone must have thought about making a round bread, and whether to use wheat instead of rye, and what other material would be needed. For example, if we have milk, but we want yogurt, we need milk first to be able to make it into yogurt; but milk is not yogurt yet, and yogurt is not the same as milk. The point here is, that if you ignore the relative truth, then milk would become yogurt and yogurt would become milk. And cheese would become yogurt, and milk too, just because they're also animal products. Relative truth tells you, that although something is made from milk, under certain conditions it can become butter, and under a different set of conditions it can become buttermilk, or cheese, or cream. All of them come from the same thin, milk, but different conditions make them into separate things. You can't say that buttermilk is milk, nor can you sat that skimmed milk is cream. So, all of them are relative truth. If people begin to ignore the relative truth, they start to lose the fundamental basis of emptiness.(Italics added)
So if some people say: 'Everything is only the result of mind, in the end it is all zero, so it doesn't matter, it's all the same, it's all bullshit' -- then that's exactly what it is: it's bullshit, because milk is not buttermilk and buttermilk is not cheese. Seeing this is what is meant by seeing emptiness through existence, or in other words seeing emptiness from the existence point of view, rather than from the 'empty' level. If you try to look from the 'empty' level, then everything is the same, then it doesn't matter whether what you do makes sense or not, because in the end it's going to be zero. That is the emptiness approach from the empty point of view and that gets you on the wrong track.
Update March 25/07: I can't believe Rinpoche said "bullshit"!