Because a veto only postpones future passage with a new president. There was no non-severability clause in the bill so he will let the court address the questionable parts. His oath of office does NOT include deciding unilaterally the constitutional soundness of any legislation. The idea that he is violating his oath is absurd and a straw man of wannabe dictators. Every bill is deemed unconstitutional by someone but that determination is a matter of fact and law and the constitution puts that responsibility squarely with the USSC. The SC hears cases having to do with 1st amendment issues on a regular basis and historically are very hard on restrictions. This is just one more for them to deal with.
If Bush had not already acknowledged that there are Constitutional problems with this CFR disaster, you would have a point. However, that he has done so leads him to a black and white choice. Don't tell me he doesn't have the ability to unilaterally decide that some legislation is un-constitutional and therefore veto it. That's why he has the veto power in the first place, and why so-called conservatives elected him to be the final check and balance in the legislative process.
And another thing. Even if he were to veto CFR, the fact that Bush has openly played fast and loose with my Constitutional freedoms for political purposes is enough for me to do everything I can to see to it that he is a one term president.
You won't change my mind. Go argue with a fencepost, you'll have better luck.