Native speakers of English, could you help me with my English?

I am translating a very complex book about architecture (this chapter is about famous architect Mies van der Rohe) and there are phrases that I find difficult to undestand. What does the following phrase mean 'even the young men can defend' (I know the general meaning of the individual words but the phrase sounds strange, does it simply mean "he even appeals to younger architects"?)

In architecture there is only one man whom even the young men can defend and that is Mies van der Rohe. Mies has always kept out of politics and has always taken his stand against functionalism. No one can accuse Mies's houses of looking like factories. Two factors especially make Mies's acceptance as the new architect possible. First, Mies is respected by the conservatives. Even the Kampfbund fur Deutsche Kultur has nothing against him. Secondly, Mies has just won a competition for the new building of the Reichsbank. The jury were older architects and representatives of the bank.
If (and it may be a long if) Mies should build this building it would clinch his position. A good modern Reichsbank would satisfy the new craving for monumentality, but above it all it would prove to the German intellectuals and to foreign countries that the new Germany is not bent on destroying all the splendid modern arts which have been built up in recent years.

Also what does the phrase "it may be a long if" mean? Does it mean it would take a long time to know exactly if he would build this building?