"We are tempted to say..." means that we don't want to say it, but we would like to. But of course, they have said it! - so it is a little hypocritical. Saying it in that way implies that saying so is somehow contentious - i.e saying so may cause trouble. "people have made use of, and are making use of..." means that people have used, and also are using. It is accentuating the fact that they have used it before, and are continuing to use it now. 'it' is whatever was mentioned after your '...'

"We are tempted to say that..." - this means that there is evidence which makes us want to make this conclusion. It's a fairly indirect phrase. "To make use of [something]" means to utilize it. "...people have made use of [something" means in the past, and up to the present moment. "...(people) are making use of [something" means this is also the present situation. Note: there are some English errors in the original text. Just be aware of that.

One is of past tense and other is of present tense. 'Have made' indicated past tense 'are making' is a present tense