No its not crule at all as they tend to live long happy lives in captivivty, and sometimes much longer then they would in the wild. Ask your mum were cats and dogs once not wild animals and now seem as family pets? Just because animals with fur are more popular pets they all started off wild as been introduced as family pets over the years. Reptile keeping is becoming more popular with time.
Beareded dragons are one of the best reptiles in my opinoin. Just make sure you do enough research first. I found a nice age for a beardie was around 4-6 months as still young enough to tame down and nice to handle.
Heres a list of requirements
100 watt spot bulb
42" 10.0 uv tube
UV starter unit (for large tube)
Lots of logs
Hope this helps. x