Some of you are not listening, and I pity you all.
First off, I know many vegetarians that are overweight. They follow the rules completely, as that is the doctrine of their Church or their personal doctrine. Eating too much is what gives you weight. Yes, fat or carbohydrate may be faster at accomplishing that, but ultimately, all in excess of anything including vegetables and protein will give you excess weight. One may display acute symptoms and the other chronic.
You have to be selective in your vegetables, ensuring that you eat a variety so that you aren't deficient in nutrients. Not all vegetables produce all recommended daily intake of vitamins, minerals, and amino acids. Often, one produces more of something than another. Broccoli, for instance, would give you a significant level of vitamin A and vitamin C and maybe folate, but insignificant of other vitamins.
Furthermore, excess vegetables could lead to nitrate toxicity, especially in infants:
Pharmacokinetics of Nitrate
Nitrate/Nitrite Toxicity
"Nitrates in vegetables--proposals for their limitation in Poland"
Nitrate and Infants
Nitrate is naturally occurring in vegetables, so it isn't always due to man-made influences or manure.
Vitamin A toxicity, even though in beta-carotene form it would only show in skin discoloration (i.e., orange skin). Chronic toxicity, as opposed to acute toxicity, occurs, since the conversion process to retinol is much longer.
And of course I mentioned vitamin B-12 being negligible in vegetables. It could lead to pernicious anemia. Even if one buys unpopular arguments made in regards to B-12 and vegetables, there's still an admission that some common vegetables cause damage to intestinal flora, which impairs production of B-12.
P.S. Amused, as much as I agree with you on some subjects, I would appreciate it if you provide supporting evidence to some of your argument.