Its called a decoy for a reason. You think the people who set up decoys don't think of these things?
Iran is one large construction site since they are building legitimate infrastructure, buildings and military sites simultaneously.
Not conceal all. Conceal most and throw the enemy off using decoys.
The ones that are known probably get the most air defense protection.
Undoubtedly all possible, but you'd be surprised the capabilities of modern IMINT especially with regard to spectrum's other then normal cameras. It may not be possible to scan ALL of Iran with this level of precision but with regard to suspected sites (like in Tabriz, Kermanshah, Khorromabad, etc) many different level of analysis can be made. This certainly isn't a guarantee of success but visual decoys are only so effective as they usually cannot replicate use and upkeep of an actual facility for any number of reasons.
Obviously this kind of analysis is mostly out of the reach of the "amateurs" like us.
But let's return to the specific example we're talking about which is the purported Tabriz missile silos, and to a lesser extend the facilities in places like Kermanshah and Khorromabad.
We can observe sites that we can tell, to the best of our abilities, are missile silos. This is because they are located adjacent to known missile storage locations and military depots and because they externally have physical features that would characterize them as such.IMO, it is a reasonable assumption that since they appear to be missile silos, they probably are missile silos. This isn't to say that we should rule out the possibility of them being decoys, they very well may be. But at this point, the physical evidence points to the former.
The problem with your logic that I see is that you're using an additional level of assumptions. What I mean by this is that when I see the evidence (which is the physical imagery of the sites) my position only lies on inferring one thing from that imagery. The point you're defending sees the same imagery, concedes that they look outwardly like missile silos (if they are in fact decoys, they would have to look like silos) and then goes a step further with the assumption that they must be decoys. The problem is that while this is a distinct possibility, there is no actual physical evidence for this in the imagery.
For instance, lets look at two other examples:
What if we found a military base on GE that had a motor pool, barracks, a mosque, garages and vehicles sitting on pavement. The logical conclusion would be that it is a garrison since it bears all the physical properties of one. It is possible that it could be a decoy using empty buildings and inflatable vehicles. However, like the missile silos, we can't make that assumption because there's no evidence for it. We can only observe the facility, acknowledge that it may be a decoy and conclude that it's most likely
a garrison facility.
Or how about if we were looking at a row of beige, unremarkable buildings lined up in the middle of Tehran. There could be hidden missile silos below the building or any number of things. While this may be possible it's not something that we can simply "assume" based on the possibility alone because if this were the case, then literally every single house in Iran could conceal a nuclear weapon; a precedent I'm sure no one in Iran would care to establish.