The link doesn't work, but a proper vegetarian diet does not cause weak bones, and an improper non-vegetarian diet could.
From the ADA:
Lacto-ovo-vegetarians have calcium intakes that are comparable to or higher than those of nonvegetarians
(25),
(26). Calcium intakes of vegans, however, are generally lower than those of both lacto-ovo-vegetarians and omnivores
(26). It should be noted that vegans may have lower calcium needs than nonvegetarians because diets that are low in total protein and more alkaline have been shown to have a calcium-sparing effect
(27). Furthermore, when a person's diet is low in both protein and sodium and regular weight-bearing physical activity is engaged in, his or her calcium requirements may be lower than those of a sedentary person who eats a standard Western diet. These factors, and genetic influences, may help explain variations in bone health that are independent of calcium intake.
Because calcium requirements of vegans have not been established and inadequate calcium intakes are linked to risk for osteoporosis in all women, vegans should meet the calcium requirements established for their age group by the Institute of Medicine
(28). Calcium is well absorbed from many plant foods, and vegan diets can provide adequate calcium if the diet regularly includes foods rich in calcium
(29). In addition, many new vegetarian foods are calcium-fortified. Dietary supplements are advised for vegans only if they do not meet calcium requirements from food.
Elsevier